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Apache Tomcat - HTTP/2 request headers not validated

Critical severity GitHub Reviewed Published May 12, 2026 to the GitHub Advisory Database • Updated Aug 31, 2026

Package

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

Affected versions

>= 10.1.0-M1, < 10.1.55
>= 11.0.0-M1, < 11.0.22
>= 8.5.0, < 9.0.118

Patched versions

10.1.55
11.0.22
9.0.118
maven org.apache.tomcat:tomcat (Maven)
>= 10.1.0-M1, < 10.1.55
>= 11.0.0-M1, < 11.0.22
>= 8.5.0, < 9.0.118
10.1.55
11.0.22
9.0.118
maven org.apache.tomcat:tomcat-coyote (Maven)
>= 8.5.0, < 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 9.0.0.M1 to 9.0.117
Older, unsupported versions may also be affected

Description:
HTTP/2 request headers were not validated which may have triggered
unexpected application behaviour if the application (quite reasonably)
assumed that header value exposed through the Servlet API would be
specification compliant.

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 Dawit Jeong (@dawitngoliath)

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 Aug 31, 2026

Severity

Critical

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
High
Integrity
High
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:N/UI:N/S:U/C:H/I:H/A:H

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.
(74th percentile)

Weaknesses

Improper Input Validation

The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly. Learn more on MITRE.

CVE ID

CVE-2026-41293

GHSA ID

GHSA-r29c-68gh-xp6x

Source code

Credits

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