CVE-2026-87022: Apache Tomcat: WebSocket message smuggling with per-message-deflate
Improper handling of length parameter inconsistency vulnerability in Apache Tomcat allows WebSocket message smuggling when per-message-deflate is used.
This issue affects Apache Tomcat: from 11.0.0-M1 through 11.0.25, from 10.1.0-M1 through 10.1.59, from 9.0.0.M1 through 9.0.121.
The following versions were EOS at the time the CVE was created but are known to be affected: from 8.5.0 through 8.5.100, from 7.0.56 through 7.0.109. Other unsupported versions may also be affected.
Users are recommended to upgrade to version 11.0.26, 10.1.60 or 9.1.22, 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 9.1.22
Event History
Frequently Asked Questions
Which deployments are exposed to this issue?
Deployments using per-message-deflate are exposed if they run Tomcat 11.0.0-M1 through 11.0.25, 10.1.0-M1 through 10.1.59, or 9.0.0.M1 through 9.0.121. End-of-support 8.5.0 through 8.5.100 and 7.0.56 through 7.0.109 are also known to be affected; other unsupported versions may be affected as well.
What must be present for exploitation?
The issue applies to WebSocket message handling when per-message-deflate is used. The provided information does not identify any additional authentication or access requirements.
How can I remediate the issue?
Upgrade to Apache Tomcat 11.0.26, 10.1.60, or 9.1.22, which are identified as fixing the issue. If running an unsupported release, upgrade to a supported fixed version because unsupported versions may also be affected.