diff --git a/packages/beacon-node/src/api/impl/beacon/pool/index.ts b/packages/beacon-node/src/api/impl/beacon/pool/index.ts
index f1973fef615e..170c358fe417 100644
--- a/packages/beacon-node/src/api/impl/beacon/pool/index.ts
+++ b/packages/beacon-node/src/api/impl/beacon/pool/index.ts
@@ -52,8 +52,9 @@ export function getBeaconPoolApi({
       await Promise.all(
         attestations.map(async (attestation, i) => {
           try {
+            const fork = chain.config.getForkName(chain.clock.currentSlot);
             // eslint-disable-next-line @typescript-eslint/explicit-function-return-type
-            const validateFn = () => validateApiAttestation(chain, {attestation, serializedData: null});
+            const validateFn = () => validateApiAttestation(fork, chain, {attestation, serializedData: null});
             const {slot, beaconBlockRoot} = attestation.data;
             // when a validator is configured with multiple beacon node urls, this attestation data may come from another beacon node
             // and the block hasn't been in our forkchoice since we haven't seen / processing that block
diff --git a/packages/beacon-node/src/api/impl/validator/index.ts b/packages/beacon-node/src/api/impl/validator/index.ts
index 242b6cccce9e..bc0b25a953d6 100644
--- a/packages/beacon-node/src/api/impl/validator/index.ts
+++ b/packages/beacon-node/src/api/impl/validator/index.ts
@@ -556,13 +556,14 @@ export function getValidatorApi({
 
       const seenTimestampSec = Date.now() / 1000;
       const errors: Error[] = [];
+      const fork = chain.config.getForkName(chain.clock.currentSlot);
 
       await Promise.all(
         signedAggregateAndProofs.map(async (signedAggregateAndProof, i) => {
           try {
             // TODO: Validate in batch
             // eslint-disable-next-line @typescript-eslint/explicit-function-return-type
-            const validateFn = () => validateApiAggregateAndProof(chain, signedAggregateAndProof);
+            const validateFn = () => validateApiAggregateAndProof(fork, chain, signedAggregateAndProof);
             const {slot, beaconBlockRoot} = signedAggregateAndProof.message.aggregate.data;
             // when a validator is configured with multiple beacon node urls, this attestation may come from another beacon node
             // and the block hasn't been in our forkchoice since we haven't seen / processing that block
diff --git a/packages/beacon-node/src/chain/errors/attestationError.ts b/packages/beacon-node/src/chain/errors/attestationError.ts
index fa380d048c7e..a93f5b42e439 100644
--- a/packages/beacon-node/src/chain/errors/attestationError.ts
+++ b/packages/beacon-node/src/chain/errors/attestationError.ts
@@ -154,7 +154,7 @@ export type AttestationErrorType =
   | {code: AttestationErrorCode.NOT_EXACTLY_ONE_AGGREGATION_BIT_SET}
   | {code: AttestationErrorCode.PRIOR_ATTESTATION_KNOWN; validatorIndex: ValidatorIndex; epoch: Epoch}
   | {code: AttestationErrorCode.FUTURE_EPOCH; attestationEpoch: Epoch; currentEpoch: Epoch}
-  | {code: AttestationErrorCode.PAST_EPOCH; attestationEpoch: Epoch; currentEpoch: Epoch}
+  | {code: AttestationErrorCode.PAST_EPOCH; attestationEpoch: Epoch; previousEpoch: Epoch}
   | {code: AttestationErrorCode.ATTESTS_TO_FUTURE_BLOCK; block: Slot; attestation: Slot}
   | {code: AttestationErrorCode.INVALID_SUBNET_ID; received: number; expected: number}
   | {code: AttestationErrorCode.WRONG_NUMBER_OF_AGGREGATION_BITS}
diff --git a/packages/beacon-node/src/chain/validation/aggregateAndProof.ts b/packages/beacon-node/src/chain/validation/aggregateAndProof.ts
index aa60140e2d9a..0cd96a8278ec 100644
--- a/packages/beacon-node/src/chain/validation/aggregateAndProof.ts
+++ b/packages/beacon-node/src/chain/validation/aggregateAndProof.ts
@@ -1,4 +1,5 @@
 import {toHexString} from "@chainsafe/ssz";
+import {ForkName} from "@lodestar/params";
 import {phase0, RootHex, ssz, ValidatorIndex} from "@lodestar/types";
 import {
   computeEpochAtSlot,
@@ -26,23 +27,29 @@ export type AggregateAndProofValidationResult = {
 };
 
 export async function validateApiAggregateAndProof(
+  fork: ForkName,
   chain: IBeaconChain,
   signedAggregateAndProof: phase0.SignedAggregateAndProof
 ): Promise<AggregateAndProofValidationResult> {
   const skipValidationKnownAttesters = true;
   const prioritizeBls = true;
-  return validateAggregateAndProof(chain, signedAggregateAndProof, null, {skipValidationKnownAttesters, prioritizeBls});
+  return validateAggregateAndProof(fork, chain, signedAggregateAndProof, null, {
+    skipValidationKnownAttesters,
+    prioritizeBls,
+  });
 }
 
 export async function validateGossipAggregateAndProof(
+  fork: ForkName,
   chain: IBeaconChain,
   signedAggregateAndProof: phase0.SignedAggregateAndProof,
   serializedData: Uint8Array
 ): Promise<AggregateAndProofValidationResult> {
-  return validateAggregateAndProof(chain, signedAggregateAndProof, serializedData);
+  return validateAggregateAndProof(fork, chain, signedAggregateAndProof, serializedData);
 }
 
 async function validateAggregateAndProof(
+  fork: ForkName,
   chain: IBeaconChain,
   signedAggregateAndProof: phase0.SignedAggregateAndProof,
   serializedData: Uint8Array | null = null,
@@ -87,7 +94,7 @@ async function validateAggregateAndProof(
     // [IGNORE] aggregate.data.slot is within the last ATTESTATION_PROPAGATION_SLOT_RANGE slots (with a MAXIMUM_GOSSIP_CLOCK_DISPARITY allowance)
     // -- i.e. aggregate.data.slot + ATTESTATION_PROPAGATION_SLOT_RANGE >= current_slot >= aggregate.data.slot
     // (a client MAY queue future aggregates for processing at the appropriate slot).
-    verifyPropagationSlotRange(chain, attSlot);
+    verifyPropagationSlotRange(fork, chain, attSlot);
   }
 
   // [IGNORE] The aggregate is the first valid aggregate received for the aggregator with
diff --git a/packages/beacon-node/src/chain/validation/attestation.ts b/packages/beacon-node/src/chain/validation/attestation.ts
index 3a17b3d4a0aa..bea4d060e48a 100644
--- a/packages/beacon-node/src/chain/validation/attestation.ts
+++ b/packages/beacon-node/src/chain/validation/attestation.ts
@@ -1,7 +1,7 @@
 import {toHexString} from "@chainsafe/ssz";
 import {phase0, Epoch, Root, Slot, RootHex, ssz} from "@lodestar/types";
 import {ProtoBlock} from "@lodestar/fork-choice";
-import {ATTESTATION_SUBNET_COUNT, SLOTS_PER_EPOCH} from "@lodestar/params";
+import {ATTESTATION_SUBNET_COUNT, SLOTS_PER_EPOCH, ForkName, ForkSeq} from "@lodestar/params";
 import {
   computeEpochAtSlot,
   CachedBeaconStateAllForks,
@@ -56,12 +56,13 @@ const SHUFFLING_LOOK_AHEAD_EPOCHS = 1;
  * - do not prioritize bls signature set
  */
 export async function validateGossipAttestation(
+  fork: ForkName,
   chain: IBeaconChain,
   attestationOrBytes: GossipAttestation,
   /** Optional, to allow verifying attestations through API with unknown subnet */
   subnet: number
 ): Promise<AttestationValidationResult> {
-  return validateAttestation(chain, attestationOrBytes, subnet);
+  return validateAttestation(fork, chain, attestationOrBytes, subnet);
 }
 
 /**
@@ -71,11 +72,12 @@ export async function validateGossipAttestation(
  * - prioritize bls signature set
  */
 export async function validateApiAttestation(
+  fork: ForkName,
   chain: IBeaconChain,
   attestationOrBytes: ApiAttestation
 ): Promise<AttestationValidationResult> {
   const prioritizeBls = true;
-  return validateAttestation(chain, attestationOrBytes, null, prioritizeBls);
+  return validateAttestation(fork, chain, attestationOrBytes, null, prioritizeBls);
 }
 
 /**
@@ -83,6 +85,7 @@ export async function validateApiAttestation(
  * This is to avoid deserializing similar attestation multiple times which could help the gc
  */
 async function validateAttestation(
+  fork: ForkName,
   chain: IBeaconChain,
   attestationOrBytes: AttestationOrBytes,
   /** Optional, to allow verifying attestations through API with unknown subnet */
@@ -146,7 +149,7 @@ async function validateAttestation(
     // [IGNORE] attestation.data.slot is within the last ATTESTATION_PROPAGATION_SLOT_RANGE slots (within a MAXIMUM_GOSSIP_CLOCK_DISPARITY allowance)
     //  -- i.e. attestation.data.slot + ATTESTATION_PROPAGATION_SLOT_RANGE >= current_slot >= attestation.data.slot
     // (a client MAY queue future attestations for processing at the appropriate slot).
-    verifyPropagationSlotRange(chain, attestationOrCache.attestation.data.slot);
+    verifyPropagationSlotRange(fork, chain, attestationOrCache.attestation.data.slot);
   }
 
   // [REJECT] The attestation is unaggregated -- that is, it has exactly one participating validator
@@ -343,22 +346,9 @@ async function validateAttestation(
  * Accounts for `MAXIMUM_GOSSIP_CLOCK_DISPARITY`.
  * Note: We do not queue future attestations for later processing
  */
-export function verifyPropagationSlotRange(chain: IBeaconChain, attestationSlot: Slot): void {
+export function verifyPropagationSlotRange(fork: ForkName, chain: IBeaconChain, attestationSlot: Slot): void {
   // slot with future tolerance of MAXIMUM_GOSSIP_CLOCK_DISPARITY_SEC
   const latestPermissibleSlot = chain.clock.slotWithFutureTolerance(MAXIMUM_GOSSIP_CLOCK_DISPARITY_SEC);
-  const earliestPermissibleSlot = Math.max(
-    // slot with past tolerance of MAXIMUM_GOSSIP_CLOCK_DISPARITY_SEC
-    // ATTESTATION_PROPAGATION_SLOT_RANGE = SLOTS_PER_EPOCH
-    chain.clock.slotWithPastTolerance(MAXIMUM_GOSSIP_CLOCK_DISPARITY_SEC) - SLOTS_PER_EPOCH,
-    0
-  );
-  if (attestationSlot < earliestPermissibleSlot) {
-    throw new AttestationError(GossipAction.IGNORE, {
-      code: AttestationErrorCode.PAST_SLOT,
-      earliestPermissibleSlot,
-      attestationSlot,
-    });
-  }
   if (attestationSlot > latestPermissibleSlot) {
     throw new AttestationError(GossipAction.IGNORE, {
       code: AttestationErrorCode.FUTURE_SLOT,
@@ -366,6 +356,49 @@ export function verifyPropagationSlotRange(chain: IBeaconChain, attestationSlot:
       attestationSlot,
     });
   }
+
+  const earliestPermissibleSlot = Math.max(
+    // slot with past tolerance of MAXIMUM_GOSSIP_CLOCK_DISPARITY_SEC
+    // ATTESTATION_PROPAGATION_SLOT_RANGE = SLOTS_PER_EPOCH
+    chain.clock.slotWithPastTolerance(MAXIMUM_GOSSIP_CLOCK_DISPARITY_SEC) - SLOTS_PER_EPOCH,
+    0
+  );
+
+  // Post deneb the attestations are valid for current as well as previous epoch
+  // while pre deneb they are valid for ATTESTATION_PROPAGATION_SLOT_RANGE
+  //
+  // see: https://github.com/ethereum/consensus-specs/pull/3360
+  if (ForkSeq[fork] < ForkSeq.deneb) {
+    if (attestationSlot < earliestPermissibleSlot) {
+      throw new AttestationError(GossipAction.IGNORE, {
+        code: AttestationErrorCode.PAST_SLOT,
+        earliestPermissibleSlot,
+        attestationSlot,
+      });
+    }
+  } else {
+    const attestationEpoch = computeEpochAtSlot(attestationSlot);
+
+    // upper bound for current epoch is same as epoch of latestPermissibleSlot
+    const latestPermissibleCurrentEpoch = computeEpochAtSlot(latestPermissibleSlot);
+    if (attestationEpoch > latestPermissibleCurrentEpoch) {
+      throw new AttestationError(GossipAction.IGNORE, {
+        code: AttestationErrorCode.FUTURE_EPOCH,
+        currentEpoch: latestPermissibleCurrentEpoch,
+        attestationEpoch,
+      });
+    }
+
+    // lower bound for previous epoch is same as epoch of earliestPermissibleSlot
+    const earliestPermissiblePreviousEpoch = computeEpochAtSlot(earliestPermissibleSlot);
+    if (attestationEpoch < earliestPermissiblePreviousEpoch) {
+      throw new AttestationError(GossipAction.IGNORE, {
+        code: AttestationErrorCode.PAST_EPOCH,
+        previousEpoch: earliestPermissiblePreviousEpoch,
+        attestationEpoch,
+      });
+    }
+  }
 }
 
 /**
diff --git a/packages/beacon-node/src/network/processor/gossipHandlers.ts b/packages/beacon-node/src/network/processor/gossipHandlers.ts
index e3692b7fb4a3..58d4a9ea3c60 100644
--- a/packages/beacon-node/src/network/processor/gossipHandlers.ts
+++ b/packages/beacon-node/src/network/processor/gossipHandlers.ts
@@ -192,9 +192,10 @@ export function getGossipHandlers(modules: ValidatorFnsModules, options: GossipH
     [GossipType.beacon_aggregate_and_proof]: async ({serializedData}, topic, _peer, seenTimestampSec) => {
       let validationResult: AggregateAndProofValidationResult;
       const signedAggregateAndProof = sszDeserialize(topic, serializedData);
+      const {fork} = topic;
 
       try {
-        validationResult = await validateGossipAggregateAndProof(chain, signedAggregateAndProof, serializedData);
+        validationResult = await validateGossipAggregateAndProof(fork, chain, signedAggregateAndProof, serializedData);
       } catch (e) {
         if (e instanceof AttestationError && e.action === GossipAction.REJECT) {
           chain.persistInvalidSszValue(ssz.phase0.SignedAggregateAndProof, signedAggregateAndProof, "gossip_reject");
@@ -229,14 +230,17 @@ export function getGossipHandlers(modules: ValidatorFnsModules, options: GossipH
       chain.emitter.emit(routes.events.EventType.attestation, signedAggregateAndProof.message.aggregate);
     },
 
-    [GossipType.beacon_attestation]: async ({serializedData, msgSlot}, {subnet}, _peer, seenTimestampSec) => {
+    [GossipType.beacon_attestation]: async ({serializedData, msgSlot}, topic, _peer, seenTimestampSec) => {
       if (msgSlot == undefined) {
         throw Error("msgSlot is undefined for beacon_attestation topic");
       }
+      const {subnet, fork} = topic;
+
       // do not deserialize gossipSerializedData here, it's done in validateGossipAttestation only if needed
       let validationResult: AttestationValidationResult;
       try {
         validationResult = await validateGossipAttestation(
+          fork,
           chain,
           {attestation: null, serializedData, attSlot: msgSlot},
           subnet
diff --git a/packages/beacon-node/test/perf/chain/validation/aggregateAndProof.test.ts b/packages/beacon-node/test/perf/chain/validation/aggregateAndProof.test.ts
index fe8ade59cef2..3fc7efe9d675 100644
--- a/packages/beacon-node/test/perf/chain/validation/aggregateAndProof.test.ts
+++ b/packages/beacon-node/test/perf/chain/validation/aggregateAndProof.test.ts
@@ -26,7 +26,8 @@ describe("validate gossip signedAggregateAndProof", () => {
         chain.seenAggregatedAttestations["aggregateRootsByEpoch"].clear();
       },
       fn: async () => {
-        await validateApiAggregateAndProof(chain, agg);
+        const fork = chain.config.getForkName(stateSlot);
+        await validateApiAggregateAndProof(fork, chain, agg);
       },
     });
 
@@ -37,7 +38,8 @@ describe("validate gossip signedAggregateAndProof", () => {
         chain.seenAggregatedAttestations["aggregateRootsByEpoch"].clear();
       },
       fn: async () => {
-        await validateGossipAggregateAndProof(chain, agg, serializedData);
+        const fork = chain.config.getForkName(stateSlot);
+        await validateGossipAggregateAndProof(fork, chain, agg, serializedData);
       },
     });
   }
diff --git a/packages/beacon-node/test/perf/chain/validation/attestation.test.ts b/packages/beacon-node/test/perf/chain/validation/attestation.test.ts
index b9664c6f5efd..84b423dd7e62 100644
--- a/packages/beacon-node/test/perf/chain/validation/attestation.test.ts
+++ b/packages/beacon-node/test/perf/chain/validation/attestation.test.ts
@@ -23,7 +23,8 @@ describe("validate attestation", () => {
       id: `validate api attestation - ${id}`,
       beforeEach: () => chain.seenAttesters["validatorIndexesByEpoch"].clear(),
       fn: async () => {
-        await validateApiAttestation(chain, {attestation: att, serializedData: null});
+        const fork = chain.config.getForkName(stateSlot);
+        await validateApiAttestation(fork, chain, {attestation: att, serializedData: null});
       },
     });
 
@@ -31,7 +32,8 @@ describe("validate attestation", () => {
       id: `validate gossip attestation - ${id}`,
       beforeEach: () => chain.seenAttesters["validatorIndexesByEpoch"].clear(),
       fn: async () => {
-        await validateGossipAttestation(chain, {attestation: null, serializedData, attSlot: slot}, subnet);
+        const fork = chain.config.getForkName(stateSlot);
+        await validateGossipAttestation(fork, chain, {attestation: null, serializedData, attSlot: slot}, subnet);
       },
     });
   }
diff --git a/packages/beacon-node/test/spec/specTestVersioning.ts b/packages/beacon-node/test/spec/specTestVersioning.ts
index 2e967e087c69..37f08e3f9e56 100644
--- a/packages/beacon-node/test/spec/specTestVersioning.ts
+++ b/packages/beacon-node/test/spec/specTestVersioning.ts
@@ -15,7 +15,7 @@ import {DownloadTestsOptions} from "@lodestar/spec-test-util";
 const __dirname = path.dirname(fileURLToPath(import.meta.url));
 
 export const ethereumConsensusSpecsTests: DownloadTestsOptions = {
-  specVersion: "v1.4.0-alpha.3",
+  specVersion: "v1.4.0-beta.0",
   // Target directory is the host package root: 'packages/*/spec-tests'
   outputDir: path.join(__dirname, "../../spec-tests"),
   specTestsRepoUrl: "https://github.com/ethereum/consensus-spec-tests",
diff --git a/packages/beacon-node/test/unit/chain/validation/aggregateAndProof.test.ts b/packages/beacon-node/test/unit/chain/validation/aggregateAndProof.test.ts
index 54191ba34846..20300776a2ec 100644
--- a/packages/beacon-node/test/unit/chain/validation/aggregateAndProof.test.ts
+++ b/packages/beacon-node/test/unit/chain/validation/aggregateAndProof.test.ts
@@ -42,7 +42,8 @@ describe("chain / validation / aggregateAndProof", () => {
   it("Valid", async () => {
     const {chain, signedAggregateAndProof} = getValidData({});
 
-    await validateApiAggregateAndProof(chain, signedAggregateAndProof);
+    const fork = chain.config.getForkName(stateSlot);
+    await validateApiAggregateAndProof(fork, chain, signedAggregateAndProof);
   });
 
   it("BAD_TARGET_EPOCH", async () => {
@@ -188,9 +189,10 @@ describe("chain / validation / aggregateAndProof", () => {
     signedAggregateAndProof: phase0.SignedAggregateAndProof,
     errorCode: AttestationErrorCode
   ): Promise<void> {
+    const fork = chain.config.getForkName(stateSlot);
     const serializedData = ssz.phase0.SignedAggregateAndProof.serialize(signedAggregateAndProof);
     await expectRejectedWithLodestarError(
-      validateGossipAggregateAndProof(chain, signedAggregateAndProof, serializedData),
+      validateGossipAggregateAndProof(fork, chain, signedAggregateAndProof, serializedData),
       errorCode
     );
   }
diff --git a/packages/beacon-node/test/unit/chain/validation/attestation.test.ts b/packages/beacon-node/test/unit/chain/validation/attestation.test.ts
index 6296ecb4c6fc..f28f62abc229 100644
--- a/packages/beacon-node/test/unit/chain/validation/attestation.test.ts
+++ b/packages/beacon-node/test/unit/chain/validation/attestation.test.ts
@@ -52,7 +52,8 @@ describe("chain / validation / attestation", () => {
   it("Valid", async () => {
     const {chain, attestation} = getValidData();
 
-    await validateApiAttestation(chain, {attestation, serializedData: null});
+    const fork = chain.config.getForkName(stateSlot);
+    await validateApiAttestation(fork, chain, {attestation, serializedData: null});
   });
 
   it("INVALID_SERIALIZED_BYTES_ERROR_CODE", async () => {
@@ -276,7 +277,8 @@ describe("chain / validation / attestation", () => {
     attestationOrBytes: ApiAttestation,
     errorCode: string
   ): Promise<void> {
-    await expectRejectedWithLodestarError(validateApiAttestation(chain, attestationOrBytes), errorCode);
+    const fork = chain.config.getForkName(stateSlot);
+    await expectRejectedWithLodestarError(validateApiAttestation(fork, chain, attestationOrBytes), errorCode);
   }
 
   async function expectGossipError(
@@ -285,7 +287,11 @@ describe("chain / validation / attestation", () => {
     subnet: number,
     errorCode: string
   ): Promise<void> {
-    await expectRejectedWithLodestarError(validateGossipAttestation(chain, attestationOrBytes, subnet), errorCode);
+    const fork = chain.config.getForkName(stateSlot);
+    await expectRejectedWithLodestarError(
+      validateGossipAttestation(fork, chain, attestationOrBytes, subnet),
+      errorCode
+    );
   }
 });
 
diff --git a/packages/state-transition/src/block/processAttestationPhase0.ts b/packages/state-transition/src/block/processAttestationPhase0.ts
index 6e7ae506dc93..248ba83b4ed2 100644
--- a/packages/state-transition/src/block/processAttestationPhase0.ts
+++ b/packages/state-transition/src/block/processAttestationPhase0.ts
@@ -1,7 +1,7 @@
 import {toHexString} from "@chainsafe/ssz";
-import {phase0, ssz} from "@lodestar/types";
+import {Slot, phase0, ssz} from "@lodestar/types";
 
-import {MIN_ATTESTATION_INCLUSION_DELAY, SLOTS_PER_EPOCH} from "@lodestar/params";
+import {MIN_ATTESTATION_INCLUSION_DELAY, SLOTS_PER_EPOCH, ForkSeq} from "@lodestar/params";
 import {computeEpochAtSlot} from "../util/index.js";
 import {CachedBeaconStatePhase0, CachedBeaconStateAllForks} from "../types.js";
 import {isValidIndexedAttestation} from "./index.js";
@@ -22,7 +22,7 @@ export function processAttestationPhase0(
   const slot = state.slot;
   const data = attestation.data;
 
-  validateAttestation(state, attestation);
+  validateAttestation(ForkSeq.phase0, state, attestation);
 
   const pendingAttestation = ssz.phase0.PendingAttestation.toViewDU({
     data: data,
@@ -56,7 +56,11 @@ export function processAttestationPhase0(
   }
 }
 
-export function validateAttestation(state: CachedBeaconStateAllForks, attestation: phase0.Attestation): void {
+export function validateAttestation(
+  fork: ForkSeq,
+  state: CachedBeaconStateAllForks,
+  attestation: phase0.Attestation
+): void {
   const {epochCtx} = state;
   const slot = state.slot;
   const data = attestation.data;
@@ -80,7 +84,9 @@ export function validateAttestation(state: CachedBeaconStateAllForks, attestatio
         `targetEpoch=${data.target.epoch} computedEpoch=${computedEpoch}`
     );
   }
-  if (!(data.slot + MIN_ATTESTATION_INCLUSION_DELAY <= slot && slot <= data.slot + SLOTS_PER_EPOCH)) {
+
+  // post deneb, the attestations are valid till end of next epoch
+  if (!(data.slot + MIN_ATTESTATION_INCLUSION_DELAY <= slot && isTimelyTarget(fork, slot - data.slot))) {
     throw new Error(
       "Attestation slot not within inclusion window: " +
         `slot=${data.slot} window=${data.slot + MIN_ATTESTATION_INCLUSION_DELAY}..${data.slot + SLOTS_PER_EPOCH}`
@@ -96,6 +102,16 @@ export function validateAttestation(state: CachedBeaconStateAllForks, attestatio
   }
 }
 
+// Modified https://github.com/ethereum/consensus-specs/pull/3360
+export function isTimelyTarget(fork: ForkSeq, inclusionDistance: Slot): boolean {
+  // post deneb attestation is valid till end of next epoch for target
+  if (fork >= ForkSeq.deneb) {
+    return true;
+  } else {
+    return inclusionDistance <= SLOTS_PER_EPOCH;
+  }
+}
+
 export function checkpointToStr(checkpoint: phase0.Checkpoint): string {
   return `${toHexString(checkpoint.root)}:${checkpoint.epoch}`;
 }
diff --git a/packages/state-transition/src/block/processAttestations.ts b/packages/state-transition/src/block/processAttestations.ts
index a2976e6491c3..2b132fa22e0b 100644
--- a/packages/state-transition/src/block/processAttestations.ts
+++ b/packages/state-transition/src/block/processAttestations.ts
@@ -18,6 +18,6 @@ export function processAttestations(
       processAttestationPhase0(state as CachedBeaconStatePhase0, attestation, verifySignatures);
     }
   } else {
-    processAttestationsAltair(state as CachedBeaconStateAltair, attestations, verifySignatures);
+    processAttestationsAltair(fork, state as CachedBeaconStateAltair, attestations, verifySignatures);
   }
 }
diff --git a/packages/state-transition/src/block/processAttestationsAltair.ts b/packages/state-transition/src/block/processAttestationsAltair.ts
index a77a6d1de0bd..cabe28b88b27 100644
--- a/packages/state-transition/src/block/processAttestationsAltair.ts
+++ b/packages/state-transition/src/block/processAttestationsAltair.ts
@@ -13,12 +13,13 @@ import {
   TIMELY_TARGET_FLAG_INDEX,
   TIMELY_TARGET_WEIGHT,
   WEIGHT_DENOMINATOR,
+  ForkSeq,
 } from "@lodestar/params";
 import {increaseBalance, verifySignatureSet} from "../util/index.js";
 import {CachedBeaconStateAltair} from "../types.js";
 import {RootCache} from "../util/rootCache.js";
 import {getAttestationWithIndicesSignatureSet} from "../signatureSets/indexedAttestation.js";
-import {checkpointToStr, validateAttestation} from "./processAttestationPhase0.js";
+import {checkpointToStr, isTimelyTarget, validateAttestation} from "./processAttestationPhase0.js";
 
 const PROPOSER_REWARD_DOMINATOR = ((WEIGHT_DENOMINATOR - PROPOSER_WEIGHT) * WEIGHT_DENOMINATOR) / PROPOSER_WEIGHT;
 
@@ -29,6 +30,7 @@ const TIMELY_HEAD = 1 << TIMELY_HEAD_FLAG_INDEX;
 const SLOTS_PER_EPOCH_SQRT = intSqrt(SLOTS_PER_EPOCH);
 
 export function processAttestationsAltair(
+  fork: ForkSeq,
   state: CachedBeaconStateAltair,
   attestations: phase0.Attestation[],
   verifySignature = true
@@ -44,7 +46,7 @@ export function processAttestationsAltair(
   for (const attestation of attestations) {
     const data = attestation.data;
 
-    validateAttestation(state, attestation);
+    validateAttestation(fork, state, attestation);
 
     // Retrieve the validator indices from the attestation participation bitfield
     const committeeIndices = epochCtx.getBeaconCommittee(data.slot, data.index);
@@ -63,7 +65,13 @@ export function processAttestationsAltair(
     const inCurrentEpoch = data.target.epoch === currentEpoch;
     const epochParticipation = inCurrentEpoch ? state.currentEpochParticipation : state.previousEpochParticipation;
 
-    const flagsAttestation = getAttestationParticipationStatus(data, stateSlot - data.slot, epochCtx.epoch, rootCache);
+    const flagsAttestation = getAttestationParticipationStatus(
+      fork,
+      data,
+      stateSlot - data.slot,
+      epochCtx.epoch,
+      rootCache
+    );
 
     // For each participant, update their participation
     // In epoch processing, this participation info is used to calculate balance updates
@@ -121,6 +129,7 @@ export function processAttestationsAltair(
  * https://github.com/ethereum/consensus-specs/blob/v1.1.10/specs/altair/beacon-chain.md#get_attestation_participation_flag_indices
  */
 export function getAttestationParticipationStatus(
+  fork: ForkSeq,
   data: phase0.AttestationData,
   inclusionDelay: number,
   currentEpoch: Epoch,
@@ -152,7 +161,7 @@ export function getAttestationParticipationStatus(
 
   let flags = 0;
   if (isMatchingSource && inclusionDelay <= SLOTS_PER_EPOCH_SQRT) flags |= TIMELY_SOURCE;
-  if (isMatchingTarget && inclusionDelay <= SLOTS_PER_EPOCH) flags |= TIMELY_TARGET;
+  if (isMatchingTarget && isTimelyTarget(fork, inclusionDelay)) flags |= TIMELY_TARGET;
   if (isMatchingHead && inclusionDelay === MIN_ATTESTATION_INCLUSION_DELAY) flags |= TIMELY_HEAD;
 
   return flags;
diff --git a/packages/state-transition/src/slot/upgradeStateToAltair.ts b/packages/state-transition/src/slot/upgradeStateToAltair.ts
index a7af38c8f068..0afa43930ef0 100644
--- a/packages/state-transition/src/slot/upgradeStateToAltair.ts
+++ b/packages/state-transition/src/slot/upgradeStateToAltair.ts
@@ -1,5 +1,6 @@
 import {CompositeViewDU} from "@chainsafe/ssz";
 import {ssz} from "@lodestar/types";
+import {ForkSeq} from "@lodestar/params";
 import {CachedBeaconStatePhase0, CachedBeaconStateAltair} from "../types.js";
 import {newZeroedArray, RootCache} from "../util/index.js";
 import {getNextSyncCommittee} from "../util/syncCommittee.js";
@@ -128,6 +129,7 @@ function translateParticipation(
   for (const attestation of pendingAttesations.getAllReadonly()) {
     const data = attestation.data;
     const attestationFlags = getAttestationParticipationStatus(
+      ForkSeq.altair,
       data,
       attestation.inclusionDelay,
       epochCtx.epoch,
diff --git a/packages/state-transition/test/perf/block/processAttestation.test.ts b/packages/state-transition/test/perf/block/processAttestation.test.ts
index d1dea1ff15bd..673b0e17430f 100644
--- a/packages/state-transition/test/perf/block/processAttestation.test.ts
+++ b/packages/state-transition/test/perf/block/processAttestation.test.ts
@@ -72,7 +72,12 @@ describe("altair processAttestation", () => {
         return {state: stateCloned, attestations};
       },
       fn: ({state, attestations}) => {
-        processAttestationsAltair(state as CachedBeaconStateAltair, attestations, false);
+        processAttestationsAltair(
+          state.config.getForkSeq(state.slot),
+          state as CachedBeaconStateAltair,
+          attestations,
+          false
+        );
         state.commit();
         // After processAttestations normal case vc 250_000 it has to do 6802 hash64 ops
         // state.hashTreeRoot();