DOM Use-After-Free Vulnerability in Firefox

Executive Summary

CVE-2026-84121 is a sandbox escape vulnerability caused by a use-after-free flaw in the DOM: Security component of Firefox. This means an attacker could exploit memory corruption to bypass security restrictions and potentially execute arbitrary code on affected systems.

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Detection Guidance

Check Firefox version with 'firefox --version' or 'about:support' in Firefox. If using ESR, verify version is 115.40, 140.15, or 153.2 or higher. Monitor for unusual processes or network activity indicating sandbox escape attempts.

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Impact Analysis

This vulnerability allows attackers to bypass security restrictions, potentially leading to unauthorized code execution. If exploited, it could compromise sensitive data, install malware, or give attackers control over the affected system.

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Compliance Impact

The provided CVE data does not specify direct impacts on compliance with standards like GDPR or HIPAA. However, sandbox escape vulnerabilities can potentially lead to unauthorized data access or execution of arbitrary code, which may violate data protection requirements under GDPR (e.g., unauthorized processing) or HIPAA (e.g., unauthorized access to protected health information).

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Mitigation Strategies

Update Firefox to version 155 or higher, or Firefox ESR to 115.40, 140.15, or 153.2 or higher immediately. Disable unnecessary Firefox features and restrict user permissions until patched.

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