Vulnerability · Published Sep 23, 2026 · Assigned by apache
CVE-2026-78437Apache Tomcat: HTTP/2 DoS via malformed request
High 7.3
In plain English
A high-severity security flaw 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 44% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
Incomplete cleanup vulnerability in Apache Tomcat allows a malformed request to potentially (depends on timing) cause one request from another user to fail. This issue affects Apache Tomcat: from 11.0.19 through 11.0.25, from 10.1.53 through 10.1.59, from 9.0.116 through 9.0.121. Users are recommended to upgrade to version 11.0.26, 10.1.60 or 9.0.122, which fix the issue.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | tomcat10 | no fix listed | DEBIAN-CVE-2026-78437 |
| Debian:13 | tomcat10 | no fix listed | DEBIAN-CVE-2026-78437 |
| Debian:14 | tomcat10 | 10.1.60-1 | DEBIAN-CVE-2026-78437 |
| Debian:13 | tomcat11 | no fix listed | DEBIAN-CVE-2026-78437 |
| Debian:14 | tomcat11 | no fix listed | DEBIAN-CVE-2026-78437 |
| Debian:12 | tomcat9 | 9.0.70-2 | DEBIAN-CVE-2026-78437 |
| Debian:13 | tomcat9 | 9.0.70-2 | DEBIAN-CVE-2026-78437 |
| Debian:14 | tomcat9 | 9.0.70-2 | DEBIAN-CVE-2026-78437 |
| Ubuntu:24.04:LTS | tomcat10 | no fix listed | UBUNTU-CVE-2026-78437 |
| Ubuntu:26.04:LTS | tomcat10 | no fix listed | UBUNTU-CVE-2026-78437 |
| Ubuntu:26.10 | tomcat10 | no fix listed | UBUNTU-CVE-2026-78437 |
| Ubuntu:26.04:LTS | tomcat11 | no fix listed | UBUNTU-CVE-2026-78437 |
| Ubuntu:26.10 | tomcat11 | no fix listed | UBUNTU-CVE-2026-78437 |
| Ubuntu:24.04:LTS | tomcat9 | no fix listed | UBUNTU-CVE-2026-78437 |
| Ubuntu:26.04:LTS | tomcat9 | no fix listed | UBUNTU-CVE-2026-78437 |
| Ubuntu:26.10 | tomcat9 | no fix listed | UBUNTU-CVE-2026-78437 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Apache Software Foundation | Apache Tomcat | 11.0.19 – through 11.0.2510.1.53 – through 10.1.599.0.116 – through 9.0.121 |
Weakness: CWE-459 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L