CVE-2026-42498 Apache Tomcat: WebSocket authentication header exposure

What is CVE-2026-42498?

CVE-2026-42498 is a high-severity vulnerability in Apache Tomcat, published on 12 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

Exposure of HTTP Authentication Header to unexpected hosts during WebSocket authentication vulnerability in Apache Tomcat.

This issue affects Apache Tomcat: from 11.0.0-M1 through 11.0.21, from 10.1.0-M1 through 10.1.54, from 9.0.2 through 9.0.117, from 8.5.24 through 8.5.100, from 7.0.83 through 7.0.109.

Users are recommended to upgrade to version 11.0.22, 10.1.55 or 9.0.118, which fix the issue.

Weakness: CWE-200

Which versions are affected by CVE-2026-42498?

19 open source packages ship an affected version, including org.apache.tomcat.embed:tomcat-embed-core, tomcat and org.apache.tomcat:tomcat. It affects 1 product.

Products include Apache Tomcat.

How do I fix CVE-2026-42498?

Upgrade org.apache.tomcat.embed:tomcat-embed-core to a fixed version for your release line: 9.0.118, 10.1.55 or 11.0.22.

Is CVE-2026-42498 being exploited?

There is no known exploitation of CVE-2026-42498 in the wild and no public exploit code.

Other vulnerabilities in Apache Tomcat

• CVE-2025-24813 Apache Tomcat Path Equivalence Exploited Critical 10.0
• CVE-2016-8735 Apache Tomcat Remote Code Execution Exploited Critical 9.8
• CVE-2017-12617 Apache Tomcat Remote Code Execution Exploited High 8.1
• CVE-2017-12615 Apache Tomcat on Windows Remote Code Execution Exploited High 8.1
• CVE-2026-34486 Apache Tomcat Missing Encryption of Sensitive Data Exploited High 7.5

All Apache Tomcat vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as BIT-tomcat-2026-42498, CLEANSTART-2026-BN96016, CLEANSTART-2026-YT48250, DEBIAN-CVE-2026-42498, GHSA-fv25-8xcx-gqjc, MINI-p237-63jj-h6g6 and 2 more.