Mozilla has released Firefox 135.0.1, a stability and security update addressing a high-severity memory safety vulnerability (CVE-2025-1414) that exposed users to potential remote code execution (RCE) attacks.
The patch resolves critical flaws in Firefox 135.0, which could have allowed attackers to exploit memory corruption and compromise systems.
This release underscores Mozilla’s ongoing efforts to mitigate browser vulnerabilities amid escalating cyber threats targeting web infrastructure.
CVE-2025-1414: Overview of the Vulnerability
The vulnerability, classified as CWE-119 (Memory Corruption), stemmed from improper boundary checks during HTML content processing.
Attackers could craft malicious websites to trigger memory corruption, enabling arbitrary code execution on unpatched systems.
Memory safety bugs in Firefox 135.0’s codebase showed clear evidence of exploitable memory corruption, with Mozilla acknowledging that sophisticated threat actors could weaponize these flaws to bypass security protocols and hijack user sessions.
The Common Vulnerability Scoring System (CVSS v4.0) rated this flaw 6.1 (High) due to its network-based exploitation vector and potential for full system compromise.
Andrew McCreight, the Mozilla engineer credited with identifying the issue, noted that the flaws were rooted in Firefox’s handling of JavaScript and DOM events, which inadvertently allowed cross-compartment memory access.
Such vulnerabilities are particularly dangerous in browsers, where sandboxing mechanisms are designed to isolate processes.
Successful exploitation could lead to credential theft, malware deployment, or lateral movement within enterprise networks.
Update Highlights and Additional Fixes
Beyond patching CVE-2025-1414, Firefox 135.0.1 resolves several functional bugs impacting user experience:
- Unresponsive Drop-Down Menus: Sites relying on specific mousemove event behaviors faced usability issues, now rectified through revised event-handling logic.
- Anchor Tag Scrolling Errors: Improper scroll positioning when navigating via anchor tags was corrected by refining layout recalibration processes.
- Session Restoration Failures: A regression preventing users from restoring closed windows/tabs after upgrading from older Firefox versions was addressed by fixing migration script conflicts.
Mozilla also enhanced security for users with custom search engines, resolving crashes caused by oversized icon files during updates. These fixes, while less severe than the memory safety patches, highlight the browser’s iterative approach to balancing performance and security.
Mitigation and Best Practices
Users are urged to update immediately via Menu > Help > About Firefox or download the latest build from Mozilla’s official channels.
Enterprises should prioritize deploying the patch across endpoints, particularly for systems handling sensitive data.
Administrators can further mitigate risks by restricting access to untrusted websites and employing network segmentation to limit lateral movement post-exploitation.
For developers, this incident reiterates the importance of rigorous fuzz testing and static analysis to identify memory handling errors before deployment.
Meanwhile, end-users must remain vigilant, ensuring automatic updates are enabled to receive critical fixes promptly.
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