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Jetty Utility Servlets ConcatServlet Double Decoding Information Disclosure Vulnerability

Moderate
waynebeaton published GHSA-gwcr-j4wh-j3cq Jun 9, 2021

Package

maven org.eclipse.jetty:jetty-servlets (Maven)

Affected versions

<= 9.4.40, <= 10.0.2, <= 11.0.2

Patched versions

9.4.41, 10.0.3, 11.0.3

Description

Requests to the ConcatServlet and WelcomeFilter are able to access protected resources within the WEB-INF directory. For example a request to the ConcatServlet with a URI of /concat?/%2557EB-INF/web.xml can retrieve the web.xml file. This can reveal sensitive information regarding the implementation of a web application.

This occurs because both ConcatServlet and WelcomeFilter decode the supplied path to verify it is not within the WEB-INF or META-INF directories. It then uses this decoded path to call RequestDispatcher which will also do decoding of the path. This double decoding allows paths with a doubly encoded WEB-INF to bypass this security check.

Impact

This affects all versions of ConcatServlet and WelcomeFilter in versions before 9.4.41, 10.0.3 and 11.0.3.

Workarounds

If you cannot update to the latest version of Jetty, you can instead deploy your own version of the ConcatServlet and/or the WelcomeFilter by using the code from the latest version of Jetty.

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
None
User interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
None
Availability
None

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:N/UI:N/S:U/C:L/I:N/A:N

CVE ID

CVE-2021-28169

Weaknesses

Credits