CVE-2011-2981 in Firefox
Summary
by MITRE
The event-management implementation in Mozilla Firefox before 3.6.20, SeaMonkey 2.x, Thunderbird 3.x before 3.1.12, and possibly other products does not properly select the context for script to run in, which allows remote attackers to bypass the Same Origin Policy or execute arbitrary JavaScript code with chrome privileges via a crafted web site.
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Analysis
by VulDB Data Team • 11/18/2021
The vulnerability described in CVE-2011-2981 represents a critical security flaw in the event management systems of several Mozilla applications including Firefox 3.6.x series, SeaMonkey 2.x, and Thunderbird 3.x. This issue stems from improper context selection during script execution, specifically affecting how the browser handles cross-origin resource sharing and privilege escalation. The flaw exists in the core implementation of event handling mechanisms that govern how JavaScript code executes within different security contexts. When a malicious website attempts to exploit this vulnerability, it can manipulate the execution environment to bypass fundamental web security policies that normally protect users from unauthorized access to sensitive browser components. The vulnerability particularly impacts the Same Origin Policy implementation which serves as a cornerstone of web security by preventing scripts from one origin from accessing resources from another origin without proper authorization. This weakness allows attackers to execute code with elevated privileges that should normally be restricted to the browser's chrome environment, where privileged operations are typically confined.
The technical nature of this vulnerability can be classified under CWE-94, which describes "Improper Control of Generation of Code" or "Code Injection," specifically manifesting as a failure to properly isolate execution contexts for scripts. The flaw operates at the intersection of browser security architecture and event handling systems, where the improper selection of execution context enables attackers to inject malicious code that executes with chrome privileges rather than the restricted user privileges typically applied to web content. Attackers can craft malicious websites that exploit this vulnerability by manipulating event handlers to execute code in a privileged context, effectively bypassing the security boundaries that separate user content from browser internals. The exploitation requires a carefully constructed web page that leverages the event management implementation to force script execution in an inappropriate security context, thereby undermining the fundamental security model that browsers employ to isolate potentially malicious code from sensitive operations.
The operational impact of this vulnerability extends beyond simple privilege escalation as it fundamentally compromises the security model of affected browsers. When successfully exploited, attackers can execute arbitrary JavaScript code with chrome privileges, which provides access to sensitive browser functions and potentially allows for full system compromise. This vulnerability enables attackers to perform actions such as reading and modifying browser internals, accessing user data, manipulating browser settings, and potentially executing arbitrary commands on the underlying system. The risk is particularly severe because it affects multiple Mozilla products simultaneously, amplifying the potential attack surface. Users visiting malicious websites could unknowingly expose their systems to complete compromise without any visible indication of the attack. The vulnerability also poses significant risks to enterprise environments where users may be browsing untrusted websites or where the browser is used for sensitive operations. The lack of proper context isolation means that even seemingly benign websites could serve as vectors for sophisticated attacks that leverage this flaw to gain elevated system access.
Mitigation strategies for CVE-2011-2981 primarily focus on immediate software updates and browser security hardening measures. Organizations should prioritize updating all affected Mozilla products to their patched versions, specifically Firefox 3.6.20, SeaMonkey 2.1.12, and Thunderbird 3.1.12, which contain the necessary fixes to properly implement context selection for script execution. Additionally, implementing browser security policies such as content security policy headers, disabling unnecessary browser features, and using security extensions can provide additional layers of protection. Network-level mitigations including web application firewalls and content filtering systems can help detect and block malicious content targeting this vulnerability. Users should be educated about the risks of visiting untrusted websites and the importance of keeping their browser software updated. The vulnerability also highlights the importance of proper input validation and context management in browser security architecture, as outlined in the ATT&CK framework under techniques related to privilege escalation and code injection. Organizations should conduct regular security assessments to identify similar vulnerabilities in their browser environments and implement comprehensive patch management procedures to ensure timely remediation of security flaws.