[SECURITY] CVE-2026-24733 Apache Tomcat - Security constraint bypass with HTTP/0.9

Mark Thomas <[email protected]> Tue, 17 Feb 2026 18:20:30 +0000
Newsgroups gmane.comp.jakarta.tomcat.user,gmane.comp.apache.incubator.ranger.devel,gmane.comp.apache.maven.announce
Message-ID <9ce1557e-0a76-4398-9e27-f6e6f9186cb0__39918.1486385473$1771352590$gmane$org@apache.org>
CVE-2026-24733 Apache Tomcat - Security constraint bypass with HTTP/0.9

Severity: Low

Vendor: The Apache Software Foundation

Versions Affected:
Apache Tomcat 11.0.0-M1 to 11.0.14
Apache Tomcat 10.1.0-M1 to 10.1.49
Apache Tomcat 9.0.0.M1 to 9.0.112
Older, EOL versions are also be affected

Description:
Tomcat did not limit HTTP/0.9 requests to the GET method. If a security 
constraint was configured to allow HEAD requests to a URI but deny GET 
requests, the user could bypass that constraint on GET requests by 
sending a (specification invalid) HEAD request using HTTP/0.9.

Mitigation:
Users of the affected versions should apply one of the following
mitigations:
- Upgrade to Apache Tomcat 11.0.15 or later
- Upgrade to Apache Tomcat 10.1.50 or later
- Upgrade to Apache Tomcat 9.0.113 or later

Credit:
This issue was identified by the Apache Tomcat security team

History:
2026-02-17 Original advisory

References:
[1] https://tomcat.apache.org/security-11.html
[2] https://tomcat.apache.org/security-10.html
[3] https://tomcat.apache.org/security-9.html