Analysis Summary

Mozilla has released a critical security update for Firefox, addressing a high-severity vulnerability tracked as CVE-2025-3608. This vulnerability resides in the browser’s nsHttpTransaction component, which manages HTTP network communications between Firefox and web servers. The flaw stems from a race condition, a concurrency issue where multiple threads access shared memory simultaneously without proper synchronization. If exploited, this can cause memory corruption, potentially enabling attackers to execute arbitrary code on affected systems. The issue has been fixed in Firefox version 137.0.2, and users running earlier versions are at risk.

The vulnerability was discovered by a Researcher who uses automated testing methods to detect software bugs by inputting unexpected or malformed data into the browser’s components. Their tools, including the Grizzly framework and Domino, identified this flaw before it could be exploited in the wild. Mozilla’s proactive fuzzing approach demonstrates the effectiveness of automated bug discovery techniques in securing complex software environments like web browsers, which are common targets for cyberattacks.

According to Mozilla’s security advisory, this race condition could result in memory being accessed after it’s been freed or while it’s still being modified by another thread, creating an exploitable state. The vulnerability has been rated 8.1 on the CVSS 3.0 scale, categorizing it as high-severity. Although it requires complex conditions to exploit (Attack Complexity: High), it needs no user privileges and no user interaction, significantly increasing its risk level. If successfully exploited, it could lead to the total compromise of confidentiality, integrity, and availability of the affected system.

Mozilla strongly urges all users to update to Firefox 137.0.2 immediately across all supported platforms to mitigate this threat. To check your Firefox version, users can navigate to the menu > Help > About Firefox. This update is particularly important for enterprise environments, where unpatched vulnerabilities can be exploited at scale. Mozilla also continues to support its bug bounty program, encouraging researchers to responsibly report vulnerabilities and helping ensure threats like CVE-2025-3608 are addressed before malicious actors can take advantage.

Impact

• Code Execution
• Gain Access

Indicators of Compromise

CVE

• CVE-2025-3608

Affected Vendors

Remediation

• Update Firefox immediately to version 137.0.2 or later to patch the vulnerability.
• Apply the update across all operating systems and devices where Firefox is installed.
• Organizations should prioritize patching in enterprise environments as part of regular security maintenance.
• Enable automatic updates in Firefox settings to ensure timely patching in the future.
• Audit systems to ensure all endpoints using Firefox are compliant with the updated version.
• Inform users and IT staff about the importance of applying the patch, especially since no user interaction is needed for exploitation.
• Continue vulnerability scanning to confirm systems are no longer exposed.
• Consider using endpoint protection tools that can detect and block memory corruption exploits as an additional layer of defense.
• Encourage security researchers to report vulnerabilities through Mozilla’s bug bounty program for proactive defense.