CVE-2011-0082 in Firefox
Summary
by MITRE
The X.509 certificate validation functionality in Mozilla Firefox 4.0.x through 4.0.1 does not properly implement single-session security exceptions, which might make it easier for user-assisted remote attackers to spoof an SSL server via an untrusted certificate that triggers potentially unwanted local caching of documents from that server.
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Analysis
by VulDB Data Team • 01/19/2025
The vulnerability described in CVE-2011-0082 represents a critical flaw in Mozilla Firefox's certificate validation mechanism that specifically affects versions 4.0 through 4.0.1. This issue stems from improper implementation of single-session security exceptions within the X.509 certificate validation process, creating a significant security gap that could be exploited by remote attackers. The flaw manifests when users encounter SSL certificates that are not trusted by Firefox's certificate store, potentially allowing malicious actors to conduct man-in-the-middle attacks by presenting forged certificates that appear legitimate to users.
The technical implementation of this vulnerability involves Firefox's handling of certificate validation exceptions during browser sessions. When users encounter untrusted certificates, Firefox should properly validate these certificates against established trust anchors and prevent caching of content from potentially compromised servers. However, the flaw allows for improper exception handling where certificates that should trigger security warnings and prevent automatic trust establishment instead create conditions where users can be tricked into accepting untrusted certificates. This behavior creates a persistent security risk as the browser may cache documents from the compromised server, making subsequent visits more vulnerable to attack. The vulnerability specifically affects the single-session exception mechanism, which is designed to allow temporary exceptions for specific certificates during a browsing session without permanently trusting them.
The operational impact of this vulnerability extends beyond simple certificate validation issues and creates a significant attack surface for user-assisted man-in-the-middle attacks. Attackers can exploit this weakness by presenting forged SSL certificates that trigger the improper exception handling, leading to a situation where users unknowingly accept untrusted certificates. The caching behavior mentioned in the description means that once a user accepts an untrusted certificate for a particular server, subsequent connections may be vulnerable to attacks even if the certificate is no longer valid or has been revoked. This creates a persistent threat vector that can compromise user data, enable data interception, and potentially allow attackers to access sensitive information that would normally be protected by SSL/TLS encryption. The vulnerability particularly affects the trust model that Firefox implements for secure web browsing, undermining the fundamental security assumptions that users make when visiting websites.
Security professionals should note that this vulnerability aligns with CWE-295, which specifically addresses improper certificate validation and trust management in security protocols. The flaw also relates to ATT&CK technique T1059, which involves the use of web services to conduct attacks, and T1190, which covers exploitation of vulnerabilities in web browsers. Organizations should implement immediate mitigations including updating to Firefox versions that address this vulnerability, implementing network monitoring to detect unusual certificate behavior, and educating users about the importance of certificate warnings. The recommended approach involves deploying patches that correct the single-session exception handling and ensuring that certificate validation follows proper X.509 standards as defined in RFC 5280. Additionally, network administrators should consider implementing certificate transparency monitoring and regular security assessments to detect potential exploitation attempts. The vulnerability demonstrates the critical importance of proper certificate validation implementation and the potential consequences when browsers fail to maintain strict security boundaries during certificate trust decisions.