AIKIDO-2026-388833
tomcat-embed-core is vulnerable to Access Control Bypass
75
High Risk
This Affects:
tomcat-embed-coreTL;DR
tomcat-embed-core RewriteValve mishandles the [N] flag because of an off-by-one error. Rewrite processing restarts at the second rule instead of the first. The skipped first rule can be an access-control or deny rule, so a request can reach a resource that should have been blocked. The fix resets rewrite processing to the first rule.
Who does this affect?
You are affected if you are using a version that falls within the vulnerable range and RewriteValve is configured with the [N] flag.
Background info
tomcat-embed-core is vulnerable to Access Control Bypass in versions 8.5.0 - 9.0.120, 10.1.0 - 10.1.57 and 11.0.0 - 11.0.24.
How to fix this
Upgrade the org.apache.tomcat.embed:tomcat-embed-core library to the patch version.
Links
tomcat.apache.org/security-11.html#Fixed_in_Apache_Tomcat_11.0.25lists.apache.org/thread/st1dx1zyn5y7ny2s0sscmh6lrv3worr4openwall.com/lists/oss-security/2026/08/26/5
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