CVE-2006-2776 in Firefox
Summary
by MITRE
Certain privileged UI code in Mozilla Firefox and Thunderbird before 1.5.0.4 calls content-defined setters on an object prototype, which allows remote attackers to execute code at a higher privilege than intended.
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Analysis
by VulDB Data Team • 01/20/2025
This vulnerability resides in the privilege separation mechanisms of mozilla firefox and thunderbird versions prior to 1.5.0.4, representing a critical flaw in the browser's security architecture that undermines the fundamental isolation between privileged and unprivileged code execution contexts. The issue stems from how the applications handle user interface code that operates with elevated privileges while simultaneously allowing content-defined setters to be invoked on object prototypes, creating an exploitable path for malicious actors to escalate their privileges. The technical implementation involves a flaw in the prototype chain handling where privileged ui code inadvertently permits content scripts to manipulate object prototypes through setter functions, effectively bypassing the intended security boundaries that separate trusted ui components from potentially malicious web content.
The operational impact of this vulnerability is severe as it allows remote attackers to execute arbitrary code with elevated privileges, effectively transforming a regular web browsing session into a potential system compromise scenario. Attackers can craft malicious web pages that exploit this prototype manipulation vulnerability to gain access to privileged execution contexts, potentially enabling them to perform actions such as file system access, registry modification, or arbitrary code execution on the target system. This represents a classic privilege escalation attack vector that leverages the browser's own security mechanisms against itself, creating a situation where the very components designed to protect the system become the attack surface.
The vulnerability aligns with multiple cybersecurity frameworks and threat models, particularly relating to common weakness enumeration category 476 which covers null pointer dereference issues, though this specific case involves prototype manipulation rather than direct pointer handling. From an attack technique perspective, this vulnerability maps to the attack pattern known as privilege escalation through code injection, where attackers exploit flaws in application architecture to elevate their execution privileges beyond intended boundaries. The flaw demonstrates a fundamental breakdown in the security model that separates content execution from privileged operations, making it particularly dangerous in environments where users might encounter malicious web content.
Mitigation strategies for this vulnerability require immediate patching of affected browser versions, as the flaw exists in the core privilege management system and cannot be effectively addressed through configuration changes or workarounds. Organizations should ensure all firefox and thunderbird installations are updated to version 1.5.0.4 or later, where the prototype handling has been corrected to prevent content-defined setters from being invoked on privileged object prototypes. Security administrators should also implement network-based protections such as web application firewalls and content filtering systems to prevent access to known malicious sites, though these measures serve as defensive layers rather than primary solutions. The vulnerability underscores the importance of maintaining current security patches and highlights the critical need for robust privilege separation mechanisms in browser architectures, as demonstrated by the successful exploitation path that allows remote code execution through seemingly benign prototype manipulation.