CVE-2026-59083 Apache Software Foundation CVE debrief

Who should care

Users of Apache Tomcat versions from 11.0.0-M1 through 11.0.23, from 10.1.0-M1 through 10.1.56, from 9.0.0.M1 through 9.0.119, from 8.5.0 through 8.5.100, and other versions that have reached end of support. Security teams and operators managing Apache Tomcat deployments should review the vulnerability details and plan for necessary upgrades or mitigations.

Technical summary

The Improper Handling of URL Encoding (Hex Encoding) vulnerability in Apache Tomcat's rewrite valve allowed security constraint bypass for some configurations. This issue affects multiple versions of Apache Tomcat across different branches, including 11.0.0-M1 through 11.0.23, 10.1.0-M1 through 10.1.56, 9.0.0.M1 through 9.0.119, and 8.5.0 through 8.5.100. Users are recommended to upgrade to version 11.0.24, 10.1.57 or 9.0.120, which fix the issue. The vulnerability has been publicly disclosed and may be targeted by attackers.

Defensive priority

High priority for users of affected Apache Tomcat versions due to potential security constraint bypass. Immediate review and remediation are recommended to prevent potential security incidents.

Recommended defensive actions

• Upgrade to version 11.0.24, 10.1.57 or 9.0.120, which fix the issue
• Review and update configurations for security constraints
• Monitor for potential security incidents related to this vulnerability
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented

Evidence notes

Evidence from official CVE and NVD sources indicate vulnerability in Apache Tomcat's rewrite valve. Limited details available on exploitability and affected scope. Defenders should verify configurations, review security constraints, and monitor for potential security incidents related to this vulnerability. Users are advised to check their deployments against affected versions and plan for upgrades or mitigations.

Official resources