CVE-2008-5913 in SeaMonkey
Summary
by MITRE
The Math.random function in the JavaScript implementation in Mozilla Firefox 3.5.x before 3.5.10 and 3.6.x before 3.6.4, and SeaMonkey before 2.0.5, uses a random number generator that is seeded only once per browser session, 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."
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Analysis
by VulDB Data Team • 08/04/2021
The vulnerability described in CVE-2008-5913 represents a significant weakness in the cryptographic randomness implementation within Mozilla Firefox and SeaMonkey browsers. This flaw specifically affects the Math.random() function which is fundamental to JavaScript implementations across web browsers. The issue stems from the fact that the random number generator used by this function is initialized with a seed value that remains constant throughout a browser session, rather than being reseeded with fresh entropy for each invocation. This design decision fundamentally compromises the unpredictability that users and developers expect from random number generation in security-sensitive contexts.
The technical implementation of this vulnerability involves the browser's JavaScript engine maintaining a single seed value for the entire duration of a browsing session, which typically begins when the browser starts and ends when it closes. This seed value is often derived from predictable system parameters such as process IDs, timestamps, or other temporal indicators that can be reconstructed by an attacker. The vulnerability creates a deterministic pattern in what should be a cryptographically secure random sequence, making it possible for malicious actors to predict future random values based on observed sequences. This behavior directly violates the fundamental principles of cryptographic randomness as defined by NIST SP 800-90 and other security standards that require unpredictable entropy sources for security-sensitive applications.
The operational impact of this vulnerability extends beyond simple predictability issues and creates serious privacy and security concerns for users. Attackers can exploit this weakness to perform session tracking across multiple web sites, essentially creating a persistent identifier that follows users through their browsing activities. The vulnerability enables what is known as a "temporary footprint" attack where an attacker can monitor a user's browsing session and then use the predictable random sequences to manipulate user interactions. This capability is particularly dangerous for phishing attacks where attackers can generate convincing spoofed pop-up messages that appear legitimate to users, as the random numbers used in the generation process can be calculated and predicted by the malicious actor.
The implications of this vulnerability align with several tactics and techniques outlined in the MITRE ATT&CK framework, particularly those related to reconnaissance and credential access. The ability to track user sessions and predict random values falls under the category of information gathering and can be used to enhance other attacks such as session hijacking or social engineering campaigns. From a CWE perspective, this vulnerability maps to CWE-330, which addresses insufficient randomness in cryptographic operations, and CWE-284, which deals with improper access control in security-sensitive contexts. The weakness also demonstrates characteristics of CWE-124, where predictable values can be used to bypass security controls.
Mitigation strategies for this vulnerability require both immediate browser updates and defensive programming practices. Users should immediately upgrade to patched versions of Firefox 3.5.10, Firefox 3.6.4, or SeaMonkey 2.0.5, which address the random number generation seeding issue by implementing proper entropy sources for each random number generation request. Browser vendors should ensure that random number generators are properly reseeded with fresh entropy for each invocation, particularly when dealing with cryptographic or security-sensitive operations. Developers should avoid relying on Math.random() for security-sensitive purposes and instead implement proper cryptographic random number generators when unpredictable sequences are required. Additionally, organizations should monitor for potential exploitation attempts and consider implementing browser hardening measures that restrict access to potentially vulnerable APIs. The vulnerability underscores the critical importance of proper entropy management in cryptographic implementations and highlights the need for continuous security auditing of core browser components that handle random number generation.