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Apache Tomcat - WebSocket authentication header exposure

High severity GitHub Reviewed Published May 12, 2026 to the GitHub Advisory Database • Updated May 18, 2026

Package

maven org.apache.tomcat.embed:tomcat-embed-core (Maven)

Affected versions

< 9.0.118
>= 10.1.0-M1, < 10.1.55
>= 11.0.0-M1, < 11.0.22

Patched versions

9.0.118
10.1.55
11.0.22
maven org.apache.tomcat:tomcat (Maven)
< 9.0.118
>= 10.1.0-M1, < 10.1.55
>= 11.0.0-M1, < 11.0.22
9.0.118
10.1.55
11.0.22
maven org.apache.tomcat:tomcat-catalina (Maven)
< 9.0.118
>= 10.1.0-M1, < 10.1.55
>= 11.0.0-M1, < 11.0.22
9.0.118
10.1.55
11.0.22

Description

Versions Affected:
Apache Tomcat 11.0.0-M1 to 11.0.21
Apache Tomcat 10.1.0-M1 to 10.1.54
Apache Tomcat 9.0.2 to 9.0.117
Older, unsupported versions may also be affected

Description:
If a WebSocket request was redirected after authentication, Tomcat's
WebSocket client would present the most recent authentication header to
the redirect target host.

Mitigation:
Users of the affected versions should apply one of the following
mitigations:

  • Upgrade to Apache Tomcat 11.0.22 or later
  • Upgrade to Apache Tomcat 10.1.55 or later
  • Upgrade to Apache Tomcat 9.0.118 or later

Credit:
This issue was identified by lokerxx

References

Published by the National Vulnerability Database May 12, 2026
Published to the GitHub Advisory Database May 12, 2026
Reviewed May 18, 2026
Last updated May 18, 2026

Severity

High

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
Low
Availability
Low

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:L/A:L

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(30th percentile)

Weaknesses

Exposure of Sensitive Information to an Unauthorized Actor

The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information. Learn more on MITRE.

CVE ID

CVE-2026-42498

GHSA ID

GHSA-fv25-8xcx-gqjc

Source code

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