# CVE-2026-86243: Apache Tomcat Native buffer over-read in TLS handshake

Source: https://junglewise.ai/threats/cve-2026-86243-buffer-over-read-vulnerability-in-apache-tomcat-native-during-the  
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-2026-86243 · Severity: high · CVSS 7.5 · Published 2026-09-23

Apache Tomcat Native is a native library that provides high-performance I/O and SSL/TLS support for the Apache Tomcat web application server. A buffer over-read vulnerability during TLS handshake processing allows a remote attacker to crash the Java Virtual Machine, causing denial of service and application downtime.

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

## Quick answers

**Is CVE-2026-86243 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-86243 being exploited in the wild.

**How severe is CVE-2026-86243?** High severity, with a CVSS score of 7.5, published 23 September 2026.

**Which products and versions are affected?** Apache Tomcat Native 1.3.0 through 1.3.8, 2.0.0 through 2.0.15.

**Is there a fix for CVE-2026-86243?** A patch was published on 2026-09-23: Fixed in Tomcat Native 1.3.9 and 2.0.16 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-86243 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-86243?** Check whether you run Apache Tomcat Native 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

A buffer over-read vulnerability exists in Apache Tomcat Native's TLS handshake processing code, exploitable via a malicious TLS connection. The vulnerability requires network access to a service using the affected library and can be triggered during the handshake phase without authentication, resulting in a JVM crash and application unavailability. Patches are available in versions 1.3.9 and 2.0.16.

## Affected products

- Apache Tomcat Native 1.3.0 through 1.3.8, 2.0.0 through 2.0.15

## Timeline

- 2026-09-23: disclosed
- 2026-09-23: patched: Fixed in Tomcat Native 1.3.9 and 2.0.16

## References

- [https://lists.apache.org/thread/8p4jf02w54m22x0cwpq2x53w3ov8o557](https://lists.apache.org/thread/8p4jf02w54m22x0cwpq2x53w3ov8o557)
- [http://www.openwall.com/lists/oss-security/2026/09/23/31](http://www.openwall.com/lists/oss-security/2026/09/23/31)

## Related threats

- [Apache Tomcat Native race condition in client certificate verification](https://junglewise.ai/threats/cve-2026-86247-race-condition-within-a-thread-vulnerability-in-apache-tomcat)
- [Apache Tomcat Native insecure default OpenSSL options](https://junglewise.ai/threats/cve-2026-86246-initialization-of-a-resource-with-an-insecure-default)
- [Apache Tomcat improper authentication in CLIENT_CERT validation](https://junglewise.ai/threats/cve-2026-29145-apache-tomcat-improper-authentication-in-client-cert-validation)