# CVE-2026-91373: Oracle Java SE JSSE denial of service

Source: https://junglewise.ai/threats/cve-2026-91373-vulnerability-in-oracle-java-se-component-jsse-supported-versions  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-20. Updated: 2026-10-20  
License: CC BY 4.0 with a link back

CVE-2026-91373 · Severity: medium · CVSS 5.3 · Published 2026-10-20

A vulnerability in Oracle Java SE's JSSE (Java Secure Socket Extension) component allows attackers to cause partial outages by sending specially crafted TLS traffic over the network without authentication. This affects Java applications and web services that use TLS for secure communication, potentially disrupting their availability.

Technologies: [Oracle GraalVM Enterprise Edition](https://junglewise.ai/threats/technologies/graalvm-enterprise-edition), [Oracle Graalvm For Jdk](https://junglewise.ai/threats/technologies/graalvm-for-jdk), [Oracle Java SE](https://junglewise.ai/threats/technologies/java-se). Vendors: [Oracle](https://junglewise.ai/threats/vendors/oracle).

## Quick answers

**Is CVE-2026-91373 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-91373 being exploited in the wild.

**How severe is CVE-2026-91373?** Medium severity, with a CVSS score of 5.3, published 20 October 2026.

**Which products and versions are affected?** Oracle GraalVM Enterprise Edition 21.3.19.1.1; Oracle Graalvm For Jdk 17.0.20.1, 21.0.12.1; Oracle Java SE 8u503, 8u503-perf, 11.0.32.1, 17.0.20.1, 21.0.12.1, 25.0.4.1.

**Is there a fix for CVE-2026-91373?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-91373 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-91373?** Check whether you run Oracle GraalVM Enterprise Edition, Oracle Graalvm For Jdk or Oracle Java SE 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 is in the JSSE component and is easily exploitable via network-based TLS connections without requiring authentication or user interaction. An unauthenticated attacker can trigger a partial denial of service by crafting specific network packets, affecting the availability of Oracle Java SE runtimes used in web services, Java Web Start applications, and applets running untrusted code.

## Affected products

- Oracle Java SE 8u503, 8u503-perf, 11.0.32.1, 17.0.20.1, 21.0.12.1, 25.0.4.1
- Oracle GraalVM for JDK 17.0.20.1, 21.0.12.1
- Oracle GraalVM Enterprise Edition 21.3.19.1.1

## Timeline

- 2026-10-20: advisory: CVE-2026-91373 published

## References

- [https://www.oracle.com/security-alerts/cpuoct2026.html](https://www.oracle.com/security-alerts/cpuoct2026.html)

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