CVE-2026-78437: Apache Tomcat: HTTP/2 DoS via malformed request
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 Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
Apache Tomcatto a version that resolves this vulnerability.Fixed in 11.0.26 - Upgrade
Upgrade
Apache Tomcatto a version that resolves this vulnerability.Fixed in 10.1.60 - Upgrade
Upgrade
Apache Tomcatto a version that resolves this vulnerability.Fixed in 9.0.122
Event History
Frequently Asked Questions
Which Tomcat deployments are affected?
Affected releases are 11.0.19 through 11.0.25, 10.1.53 through 10.1.59, and 9.0.116 through 9.0.121. Deployments outside those listed ranges are not identified as affected by the provided advisory.
What does an attacker need to do to trigger the issue?
An attacker needs to send a malformed request. Whether it causes another user's request to fail depends on timing.
What should teams do to remediate the vulnerability?
Upgrade Tomcat to 11.0.26, 10.1.60, or 9.0.122, according to the release line in use. These versions contain the fix.