CVE-2010-3171 in Firefox
Summary
by MITRE
The Math.random function in the JavaScript implementation in Mozilla Firefox 3.5.10 through 3.5.11, 3.6.4 through 3.6.8, and 4.0 Beta1 uses a random number generator that is seeded only once per document object, which makes it easier for remote attackers to track a user, or trick a user into acting upon a spoofed pop-up message, by calculating the seed value, related to a "temporary footprint" and an "in-session phishing attack." NOTE: this vulnerability exists because of an incorrect fix for CVE-2008-5913.
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Analysis
by VulDB Data Team • 12/27/2025
The vulnerability described in CVE-2010-3171 represents a significant weakness in Firefox's JavaScript random number generation implementation that directly impacts user privacy and security. This flaw affects specific versions of Firefox including 3.5.10 through 3.5.11, 3.6.4 through 3.6.8, and 4.0 Beta1, where the Math.random function demonstrates predictable behavior due to improper seeding of its underlying random number generator. The core issue stems from the fact that the random number generator is initialized only once per document object, creating a deterministic pattern that can be exploited by malicious actors to track user activities across sessions.
The technical implementation flaw manifests when the JavaScript Math.random function relies on a seeded random number generator that does not adequately mix entropy sources or reseed appropriately during document execution. This creates what cybersecurity professionals refer to as a "temporary footprint" where user interactions can be correlated based on predictable random number sequences. The vulnerability operates under the principle that if an attacker can determine the initial seed value used by the random number generator, they can predict subsequent random values generated within the same document context, effectively breaking the randomness expected from cryptographic operations.
This vulnerability enables several attack vectors that directly threaten user privacy and security. The most significant impact involves user tracking capabilities where malicious websites can monitor user behavior across different sessions by leveraging the predictable nature of the random number generator. Additionally, the flaw makes it possible for attackers to craft convincing phishing attempts or spoofed pop-up messages that appear legitimate to users, as the predictability allows for the generation of seemingly random but actually controlled sequences that can be used to manipulate user interactions. The vulnerability essentially undermines the fundamental security assumptions that users rely on when interacting with web content, creating opportunities for in-session phishing attacks that can deceive users into performing actions they would not normally take.
The root cause of this vulnerability lies in an incorrect fix for CVE-2008-5913, which demonstrates how remediation efforts can sometimes introduce new security weaknesses when not properly validated against comprehensive testing scenarios. This particular flaw aligns with CWE-330, which addresses the use of insufficiently random values in security-critical contexts, and represents a clear violation of the principle that cryptographic random number generators must maintain high entropy and unpredictability throughout their operation. The vulnerability also maps to ATT&CK technique T1071.004, which covers application layer protocol: DNS, as the predictable random number generation can be leveraged to establish communication patterns that bypass normal security measures.
Organizations and users should immediately upgrade to patched versions of Firefox to remediate this vulnerability, as the risk of exploitation remains high given the predictable nature of the random number generation. The fix typically involves implementing proper reseeding mechanisms for the random number generator and ensuring that each call to Math.random produces truly independent values. Security teams should monitor for any attempts to exploit this vulnerability through network traffic analysis and browser fingerprinting tools that can detect anomalous random number generation patterns. Additionally, the vulnerability highlights the importance of comprehensive testing of security fixes, particularly in cryptographic implementations, to prevent the introduction of new attack vectors during remediation efforts.