CVE-2026-21945: Oracle Java SE and GraalVM denial of service in Security component

CVE-2026-21945 · Severity: high · CVSS 7.5 · Published 2026-01-20

A vulnerability in the security component of Oracle Java and GraalVM can allow an unauthenticated attacker to remotely crash or freeze the software. This issue primarily affects client-side Java deployments that run untrusted code from the internet, such as sandboxed applets. An exploit could lead to a complete denial of service, disrupting business operations and application availability.

Technologies: Oracle GraalVM Enterprise Edition, Oracle Graalvm For Jdk, Oracle Java SE, Siemens SIMATIC CN 4100. Vendors: Oracle, Siemens.

Quick answers

Is CVE-2026-21945 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-21945 being exploited in the wild.
How severe is CVE-2026-21945?
High severity, with a CVSS score of 7.5, published 20 January 2026.
Which products and versions are affected?
Oracle GraalVM Enterprise Edition 21.3.16; Oracle Graalvm For Jdk 17.0.17, 21.0.9; Oracle Java SE 8u471, 8u471-b50, 8u471-perf, 11.0.29, 17.0.17, 21.0.9, 25.0.1; Siemens SIMATIC CN 4100 All versions < V5.0.
Is there a fix for CVE-2026-21945?
A patch was published on 2026-01-21: Red Hat released security updates for OpenJDK 11 ELS Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-21945 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-21945?
Check whether you run Oracle GraalVM Enterprise Edition, Oracle Graalvm For Jdk, Oracle Java SE or one of the others listed 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 vulnerability exists in the Security component of Oracle Java SE and GraalVM related to improper certificate validation (CWE-295) and uncontrolled resource consumption (CWE-400). The flaw is easily exploitable by an unauthenticated attacker with network access via multiple protocols. Successful exploitation allows an attacker to cause a frequently repeatable crash or a hang, resulting in a complete denial of service (DoS). This vulnerability specifically impacts Java deployments that rely on the Java sandbox to run untrusted code, such as Java Web Start applications. Server-side deployments running only trusted code are generally not affected. Patches are available through Oracle's January 2026 Critical Patch Update and Red Hat's security advisories.

Affected products

  • Oracle Java SE 8u471, 8u471-b50, 8u471-perf, 11.0.29, 17.0.17, 21.0.9, 25.0.1
  • Oracle GraalVM for JDK 17.0.17, 21.0.9
  • Oracle GraalVM Enterprise Edition 21.3.16
  • Red Hat OpenJDK 11 ELS 11.0.29

Timeline

  • 2026-01-20: advisory: Initial disclosure by Oracle and NVD publication
  • 2026-01-21: patched: Red Hat released security updates for OpenJDK 11 ELS

References

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