CVE-2026-77762: Apache Tomcat: Stale HPACK emitter injects trailers into recycled pooled Request
Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition') vulnerability in Apache Tomcat allows an attacker to inject trailer fields into another HTTP/2 request.
This issue affects Apache Tomcat: from 11.0.0-M1 through 11.0.25, from 10.1.0-M1 through 10.1.59, from 9.0.39 through 9.0.121.
The following versions were EOL at the time the CVE was created but are known to be affected: from 8.5.59 through 8.5.100. Other unsupported versions may also be affected.
Users are recommended to upgrade to version 11.0.26, 10.1.60, 9.0.122, which fix the issue.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
Apache Tomcat 11.0.xto a version that resolves this vulnerability.Fixed in 11.0.26 - Upgrade
Upgrade
Apache Tomcat 10.1.xto a version that resolves this vulnerability.Fixed in 10.1.60 - Upgrade
Upgrade
Apache Tomcat 9.0.xto a version that resolves this vulnerability.Fixed in 9.0.122
Event History
Frequently Asked Questions
Which Tomcat release should I upgrade to?
Upgrade to Apache Tomcat 11.0.26, 10.1.60, or 9.0.122, depending on your supported major/minor release line. These versions fix the issue.
Are end-of-life Tomcat releases affected?
Tomcat 8.5.59 through 8.5.100 were end-of-life when the CVE was created but are known to be affected. Other unsupported versions may also be affected.
What must an attacker be able to do to exploit this issue?
The issue enables injection of trailer fields into another HTTP/2 request. The provided information does not specify additional authentication, network-position, or configuration prerequisites.