CVE-2026-86247: Apache Tomcat Native: Client certificate requirements can be down-graded

Severity: high (CVSS 7.4 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-09-23 · updated 2026-10-06
Weakness: CWE-366

Description

Race condition within a thread vulnerability in Apache Tomcat Native allowed client certificate verification requirements to be down-graded for some configurations. This issue affects Apache Tomcat Native: from 2.0.0 through 2.0.15, from 1.3.0 through 1.3.8. Unsupported versions may also be affected. Users are recommended to upgrade to version 2.0.16 or 1.3.9, which fixes the issue.

Affected products

Apache Software Foundation Apache Tomcat Native: from 1.3.0 before 1.3.9; from 2.0.0 before 2.0.16 — fixed in 1.3.9, 2.0.16

How to fix

Upgrade to a fixed version: Apache Software Foundation Apache Tomcat Native 1.3.9, 2.0.16. Check the vendor advisory for mitigations.

References

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