CVE-2006-4340 in Firefox
Summary
by MITRE
Mozilla Network Security Service (NSS) library before 3.11.3, as used in Mozilla Firefox before 1.5.0.7, Thunderbird before 1.5.0.7, and SeaMonkey before 1.0.5, when using an RSA key with exponent 3, does not properly handle extra data in a signature, which allows remote attackers to forge signatures for SSL/TLS and email certificates, a similar vulnerability to CVE-2006-4339. NOTE: on 20061107, Mozilla released an advisory stating that these versions were not completely patched by MFSA2006-60. The newer fixes for 1.5.0.7 are covered by CVE-2006-5462.
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Analysis
by VulDB Data Team • 03/13/2021
The vulnerability described in CVE-2006-4340 represents a critical cryptographic flaw within the Mozilla Network Security Service library that affected multiple Mozilla applications including Firefox, Thunderbird, and SeaMonkey. This weakness specifically impacts systems using RSA keys with exponent 3, which is a common configuration in SSL/TLS and email certificate operations. The flaw stems from improper handling of extra data within digital signatures, creating a pathway for malicious actors to exploit the cryptographic system and generate fraudulent certificates that would appear legitimate to users and applications.
The technical implementation of this vulnerability involves the manipulation of signature verification processes within the NSS library where RSA keys with exponent 3 are utilized. When processing signatures, the system fails to properly validate or strip additional data that may be appended to the signature structure, allowing attackers to inject malicious content that bypasses normal cryptographic verification procedures. This issue is particularly dangerous because it operates at the core cryptographic layer, affecting the fundamental trust mechanisms that secure web communications and email exchanges. The vulnerability aligns with CWE-327, which addresses the use of weak cryptographic algorithms and improper implementation of cryptographic functions, specifically targeting the improper handling of cryptographic data structures.
The operational impact of this vulnerability extends beyond simple certificate forgery, potentially enabling man-in-the-middle attacks, unauthorized access to secure communications, and compromise of email authentication systems. Attackers could create fake SSL certificates that would be accepted by vulnerable browsers, allowing them to intercept and modify encrypted web traffic without detection. Similarly, forged email certificates could bypass authentication mechanisms, leading to email spoofing and potential data breaches. This weakness directly relates to ATT&CK technique T1552.001, which involves the exploitation of weak cryptographic implementations to gain unauthorized access to systems and data.
The vulnerability was addressed through a series of patches released by Mozilla, though the initial fixes were not comprehensive according to the advisory issued on November 7, 2006. The subsequent release of version 1.5.0.7 included more robust fixes that resolved the underlying cryptographic implementation issues. Organizations affected by this vulnerability needed to update their Mozilla applications immediately to prevent exploitation, as the attack vector required no user interaction and could be executed remotely. The patch process specifically targeted the signature verification routines within NSS, ensuring that extra data in RSA signatures with exponent 3 would be properly validated and rejected rather than accepted as legitimate. This vulnerability highlighted the importance of proper cryptographic implementation and the need for thorough testing of security patches before deployment, as evidenced by the need for follow-up fixes referenced in CVE-2006-5462.