# CVE-2026-86248: Apache Tomcat CLIENT_CERT authentication bypass when soft fail disabled

Source: https://junglewise.ai/threats/cve-2026-86248-client-cert-authentication-does-not-fail-as-expected-for-some  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-23. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-86248 · Severity: critical · CVSS 9.8 · Published 2026-09-23

Apache Tomcat is a widely-deployed web server and servlet container used to run Java-based web applications. A flaw in how Tomcat handles client certificate authentication allows requests that should be rejected to proceed when soft-fail mode is disabled, potentially allowing unauthorized access to protected resources. An attacker can exploit this to bypass certificate-based access controls on sensitive applications.

Technologies: [Apache Tomcat](https://junglewise.ai/threats/technologies/tomcat). Vendors: [Apache](https://junglewise.ai/threats/vendors/apache).

## Quick answers

**Is CVE-2026-86248 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-86248 being exploited in the wild.

**How severe is CVE-2026-86248?** Critical severity, with a CVSS score of 9.8, published 23 September 2026.

**Which products and versions are affected?** Apache Tomcat 11.0.0-M14 through 11.0.25, 10.1.22 through 10.1.59, 9.0.92 through 9.0.121.

**Is there a fix for CVE-2026-86248?** A patch was published on 2026-09-23: Patches released: 11.0.26, 10.1.60, 9.0.122 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-86248 attacked?** It is attacked over the network, in a web application.

**Am I affected by CVE-2026-86248?** Check whether you run Apache Tomcat at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability exists in Tomcat's CLIENT_CERT authentication mechanism where certain authentication failure scenarios are not properly handled when soft-fail is disabled, resulting in requests proceeding without proper validation. The issue affects the authentication filter's enforcement logic and can be triggered via network requests to applications configured with mandatory client certificate authentication. A patch is available in Tomcat 11.0.26, 10.1.60, and 9.0.122.

## Affected products

- Apache Tomcat 11.0.0-M14 through 11.0.25, 10.1.22 through 10.1.59, 9.0.92 through 9.0.121

## Timeline

- 2026-09-23: disclosed
- 2026-09-23: patched: Patches released: 11.0.26, 10.1.60, 9.0.122

## References

- [https://lists.apache.org/thread/nmkmjp9l53y8h3oc4n8fc0bkw9dv15sk](https://lists.apache.org/thread/nmkmjp9l53y8h3oc4n8fc0bkw9dv15sk)

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