[SECURITY] CVE-2026-24880 Apache Tomcat - Request smuggling via invalid chunk extension

Mark Thomas <[email protected]> Thu, 9 Apr 2026 20:03:14 +0100
Newsgroups gmane.comp.apache.maven.announce,gmane.comp.apache.incubator.bigtop.devel,gmane.comp.jakarta.tomcat.user
Message-ID <56cd32df-f312-4efc-80ee-1250c9fdf988__35842.2310951696$1775761436$gmane$org@apache.org>
CVE-2026-24880 Apache Tomcat - Request smuggling via invalid chunk extension

Severity: Low

Vendor: The Apache Software Foundation

Versions Affected:
Apache Tomcat 11.0.0-M1 to 11.0.18
Apache Tomcat 10.1.0-M1 to 10.1.52
Apache Tomcat 9.0.0.M1 to 9.0.115
Older, EOS versions may also be affected

Description:
Tomcat did not validate that contents of HTTP/1.1 chunk extensions. This 
enabled a request smuggling attack if a reverse proxy in front of Tomcat 
allowed CRLF sequences in an otherwise valid chunk extension.

Mitigation:
Users of the affected versions should apply one of the following
mitigations:
- Upgrade to Apache Tomcat 11.0.20 or later
- Upgrade to Apache Tomcat 10.1.53 or later
- Upgrade to Apache Tomcat 9.0.116 or later

Credit:
This issue was identified by Xclow3n

History:
2026-04-09 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