CVE-2026-77762 Apache Tomcat: Stale HPACK emitter injects trailers into recycled pooled Request
An attacker can inject HTTP/2 trailer fields into other requests due to a race condition in Apache Tomcat's HPACK emitter.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-77762?
CVE-2026-77762 is a high-severity vulnerability in Apache Tomcat, published on 23 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
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.
Weakness: CWE-362
Which versions are affected by CVE-2026-77762?
1 open source package ship an affected version, including tomcat.
| Package | Affected | Fixed in |
|---|---|---|
tomcat Bitnami | From 8.56.59 | 9.0.122, 10.1.60, 11.0.26 |
How do I fix CVE-2026-77762?
Upgrade tomcat to a fixed version for your release line: 9.0.122, 10.1.60 or 11.0.26.
Is CVE-2026-77762 being exploited?
There is no known exploitation of CVE-2026-77762 in the wild and no public exploit code.
Sources
Also known as BIT-tomcat-2026-77762, DEBIAN-CVE-2026-77762, GHSA-28v4-2v86-58cc, MINI-6gq2-g7p9-wwf2, MINI-qpmw-2w7p-xg6g, MINI-rmvr-4m5g-j37v and 1 more.