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netty-handler SniHandler 16MB allocation

Moderate severity GitHub Reviewed Published Jun 20, 2023 in netty/netty • Updated Jun 24, 2024

Package

maven io.netty:netty-handler (Maven)

Affected versions

< 4.1.94.Final

Patched versions

4.1.94.Final

Description

Summary

The SniHandler can allocate up to 16MB of heap for each channel during the TLS handshake. When the handler or the channel does not have an idle timeout, it can be used to make a TCP server using the SniHandler to allocate 16MB of heap.

Details

The SniHandler class is a handler that waits for the TLS handshake to configure a SslHandler according to the indicated server name by the ClientHello record. For this matter it allocates a ByteBuf using the value defined in the ClientHello record.

Normally the value of the packet should be smaller than the handshake packet but there are not checks done here and the way the code is written, it is possible to craft a packet that makes the SslClientHelloHandler

1/ allocate a 16MB ByteBuf
2/ not fail decode method in buffer
3/ get out of the loop without an exception

The combination of this without the use of a timeout makes easy to connect to a TCP server and allocate 16MB of heap memory per connection.

Impact

If the user has no idle timeout handler configured it might be possible for a remote peer to send a client hello packet which lead the server to buffer up to 16MB of data per connection. This could lead to a OutOfMemoryError and so result in a DDOS.

References

@normanmaurer normanmaurer published to netty/netty Jun 20, 2023
Published to the GitHub Advisory Database Jun 20, 2023
Reviewed Jun 20, 2023
Published by the National Vulnerability Database Jun 22, 2023
Last updated Jun 24, 2024

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

EPSS score

0.122%
(48th percentile)

CVE ID

CVE-2023-34462

GHSA ID

GHSA-6mjq-h674-j845

Source code

Credits

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