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CVE-2026-21932: Window Pains: Breaking the Java Sandbox via AWT (CVE-2026-21932)

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Window Pains: Breaking the Java Sandbox via AWT (CVE-2026-21932)

Vulnerability ID: CVE-2026-21932
CVSS Score: 7.4
Published: 2026-01-20

A high-severity sandbox escape vulnerability in Oracle Java SE and GraalVM's AWT and JavaFX components. This flaw allows unauthenticated, remote attackers to bypass the Java SecurityManager restrictions and compromise system integrity. While technically limited to integrity violations (file modification/creation), in the hands of a creative attacker, this is functionally equivalent to full system compromise in specific client-side deployment scenarios.

TL;DR

CVE-2026-21932 is a 'Scope Changed' sandbox escape in Java's windowing toolkit (AWT/JavaFX). It allows malicious Java Web Start applications or applets to break out of the virtual machine and modify files on the host OS. While it doesn't grant direct memory reading capabilities (Confidentiality: None), the ability to overwrite system files makes it a critical threat for legacy enterprise environments relying on sandboxed Java.

Technical Details

  • Attack Vector: Network (Remote)
  • CVSS v3.1: 7.4 (High)
  • Impact: Integrity Compromise / Sandbox Escape
  • EPSS Score: 0.03% (Low probability)
  • Scope: Changed (Host OS affected)
  • Exploit Status: No public PoC

Affected Systems

  • Oracle Java SE
  • Oracle GraalVM for JDK
  • Oracle GraalVM Enterprise Edition
  • Clients using Java Web Start
  • Browsers with Java Plugin enabled (Legacy)
  • Oracle Java SE 8: < 8u471 (Fixed in: 8u471)
  • Oracle Java SE 11: < 11.0.29 (Fixed in: 11.0.29)
  • Oracle Java SE 17: < 17.0.17 (Fixed in: 17.0.17)
  • Oracle Java SE 21: < 21.0.9 (Fixed in: 21.0.9)

Mitigation Strategies

  • Disable Java Web Start and Applet support in browsers.
  • Implement Deployment Rule Sets (DRS) to whitelist only trusted internal applications.
  • Monitor endpoints for unexpected changes to startup folders or shell configuration files.

Remediation Steps:

  1. Identify all endpoints with older Java SE Runtime Environments installed.
  2. Deploy Oracle JDK/JRE 8u471, 11.0.29, 17.0.17, 21.0.9, or 25.0.1.
  3. Verify the version via command line: java -version.
  4. Restart any running Java applications to load the patched libraries.

References

Read the full report for CVE-2026-21932 on our website for more details including interactive diagrams and full exploit analysis.

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