Vulnerability · Published Sep 23, 2026 · Assigned by apache
CVE-2026-77762Apache Tomcat: Stale HPACK emitter injects trailers into recycled pooled Request
High 8.1
In plain English
A high-severity race condition in Apache Tomcat from Apache Software Foundation. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 40% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | tomcat10 | no fix listed | DEBIAN-CVE-2026-77762 |
| Debian:13 | tomcat10 | no fix listed | DEBIAN-CVE-2026-77762 |
| Debian:14 | tomcat10 | 10.1.60-1 | DEBIAN-CVE-2026-77762 |
| Debian:13 | tomcat11 | no fix listed | DEBIAN-CVE-2026-77762 |
| Debian:14 | tomcat11 | no fix listed | DEBIAN-CVE-2026-77762 |
| Debian:12 | tomcat9 | 9.0.70-2 | DEBIAN-CVE-2026-77762 |
| Debian:13 | tomcat9 | 9.0.70-2 | DEBIAN-CVE-2026-77762 |
| Debian:14 | tomcat9 | 9.0.70-2 | DEBIAN-CVE-2026-77762 |
| Ubuntu:24.04:LTS | tomcat10 | no fix listed | UBUNTU-CVE-2026-77762 |
| Ubuntu:26.04:LTS | tomcat10 | no fix listed | UBUNTU-CVE-2026-77762 |
| Ubuntu:26.10 | tomcat10 | no fix listed | UBUNTU-CVE-2026-77762 |
| Ubuntu:26.04:LTS | tomcat11 | no fix listed | UBUNTU-CVE-2026-77762 |
| Ubuntu:26.10 | tomcat11 | no fix listed | UBUNTU-CVE-2026-77762 |
| Ubuntu:24.04:LTS | tomcat9 | no fix listed | UBUNTU-CVE-2026-77762 |
| Ubuntu:26.04:LTS | tomcat9 | no fix listed | UBUNTU-CVE-2026-77762 |
| Ubuntu:26.10 | tomcat9 | no fix listed | UBUNTU-CVE-2026-77762 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Apache Software Foundation | Apache Tomcat | 11.0.0-M1 – through 11.0.2510.1.0-M1 – through 10.1.599.0.39 – through 9.0.1218.5.59 – through 8.5.100 |
Weakness: CWE-362 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H