CVE-2026-86247 Apache CVE debrief

Who should care

Defenders responsible for Apache Tomcat Native deployments should assess exposure and prioritize upgrading to the fixed versions. This includes operators, security teams, and vulnerability management teams who need to review and update configurations to ensure client certificate verification requirements are properly enforced. Defenders should also verify affected versions and configurations, and monitor for potential exploitation attempts.

Why it matters

CVE-2026-86247 is a high-severity vulnerability in Apache Tomcat Native that requires attention from defenders responsible for deployments. The vulnerability allows client certificate verification requirements to be downgraded for some configurations, potentially impacting security configurations. Defenders should prioritize upgrading to the fixed versions, specifically version 2.0.16 or 1.3.9, and verify affected versions and configurations.

• Potential downgrading of client certificate verification requirements
• Possible impact on security configurations
• Need for verification of affected versions and configurations
• Priority for upgrading to fixed versions

Technical summary

A race condition within a thread vulnerability in Apache Tomcat Native allows client certificate verification requirements to be downgraded for some configurations. This issue affects Apache Tomcat Native versions from 2.0.0 through 2.0.15 and from 1.3.0 through 1.3.8. The vulnerability has a CVSS score of 7.4 and is considered high-severity. Defenders should prioritize upgrading to the fixed versions of Apache Tomcat Native, specifically version 2.0.16 or 1.3.9, to mitigate the vulnerability. The vulnerability may impact security configurations, and defenders should review and update configurations to ensure client certificate verification requirements are properly enforced.

Defensive priority

Defenders should prioritize upgrading to the fixed versions of Apache Tomcat Native, specifically version 2.0.16 or 1.3.9, to mitigate the vulnerability.

Recommended defensive actions

• Upgrade to Apache Tomcat Native version 2.0.16 or 1.3.9
• Review and update configurations to ensure client certificate verification requirements are properly enforced
• Monitor for potential exploitation attempts
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up
• Review the supplied official advisory or CVE record to validate affected scope, severity, and vendor guidance
• Plan vendor-supported updates or mitigations through normal change control where exposure is confirmed
• Check relevant monitoring, detection, and logs for exposed assets that need extra review

Evidence notes

The CVE record and NVD vulnerability detail page provide information on the vulnerability, its impact, and recommended actions. The vulnerability affects Apache Tomcat Native versions from 2.0.0 through 2.0.15 and from 1.3.0 through 1.3.8. Evidence is limited to public CVE and NVD sources. Defenders should verify affected versions and configurations, and review security configurations.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.