Access-control bypass via RewriteValve restart off-by-one
Published Aug 25, 2026 · Updated Aug 25, 2026
Off-by-one processing in affected Apache Tomcat RewriteValve releases allows remote attackers to bypass configured access controls. When an [N] flag restarts rewriting, the valve advances its rule index and resumes at the second rule instead of reevaluating the first. Exploitation requires a deployed RewriteValve rule set that uses [N] and relies on the skipped first rule as a security control; successful requests reach resources that rule was intended to block.
Summary
What happened
Off-by-one processing in affected Apache Tomcat RewriteValve releases allows remote attackers to bypass configured access controls. When an [N] flag restarts rewriting, the valve advances its rule index and resumes at the second rule instead of reevaluating the first. Exploitation requires a deployed RewriteValve rule set that uses [N] and relies on the skipped first rule as a security control; successful requests reach resources that rule was intended to block.
The record
- CVE
- CVE-2026-65927
- Published
- Aug 25, 2026
- Updated
- Aug 25, 2026
- Vendor
- The Apache Software Foundation
- Product
- Apache Tomcat
- Classifications
- CWE-193, T1190
- Attack vector
- network
- Privileges
- Unavailable
Timeline
How it unfolded
- Aug 25, 2026CVE publishedPublication date reported by the CVE source.
- Aug 25, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=10.1.0-M1 <=10.1.57
- Affected versionversion=11.0.0-M1 <=11.0.24
- Affected versionversion=8.5.0 <=8.5.100
- Affected versionversion=9.0.0.M1 <=9.0.120
What conditions does exploitation require?
What is affected?
Published CVSS scores
No CVSS assessment is available in this record.
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Attacks
What attackers are doing with it
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Public exploit references
No public exploit references are available in this record.
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Technologies
Your stack
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Your stack
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