[SECURITY] CVE-2026-25854 Apache Tomcat - Occasionally open redirect

CVE-2026-25854 Apache Tomcat - Occasionally open redirect

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.M23 to 9.0.115
Older, EOS versions may also be affected

Description:
When a Tomcat node in a cluster with the LoadBalancerDrainingValve was 
in the disabled (draining) state, a specially crafted URL could be used 
to trigger a redirect to a URI of the attackers choice.

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 gregk4sec (https://github.com/gregk4sec)

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