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Ambiguous paths can access WEB-INF

Moderate
waynebeaton published GHSA-v7ff-8wcx-gmc5 Apr 1, 2021

Package

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

Affected versions

9.4.37.v20210219, 9.4.38.v20210224

Patched versions

9.4.39

Description

Description

Release 9.4.37 introduced a more precise implementation of RFC3986 with regards to URI decoding, together with some new compliance modes to optionally allow support of some URI that may have ambiguous interpretation within the Servlet specified API methods behaviours. The default mode allowed % encoded . characters to be excluded for URI normalisation, which is correct by the RFC, but is not assumed by common Servlet implementations.

Impact

The default compliance mode allows requests with URIs that contain %2e or %2e%2e segments to access protected resources within the WEB-INF directory. For example a request to /context/%2e/WEB-INF/web.xml can retrieve the web.xml file. This can reveal sensitive information regarding the implementation of a web application.

Workarounds

The HttpCompliance mode RFC7230_NO_AMBIGUOUS_URIS can be enabled by updating start.d/http.ini to include:

jetty.http.compliance=RFC7230_NO_AMBIGUOUS_URIS

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-2021-28164

Credits