CVE-2011-3647 in Firefox
Summary
by MITRE
The JSSubScriptLoader in Mozilla Firefox before 3.6.24 and Thunderbird before 3.1.6 does not properly handle XPCNativeWrappers during calls to the loadSubScript method in an add-on, which makes it easier for remote attackers to gain privileges via a crafted web site that leverages certain unwrapping behavior, a related issue to CVE-2011-3004.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 11/26/2021
The vulnerability identified as CVE-2011-3647 represents a critical privilege escalation flaw within the JavaScript security architecture of Mozilla Firefox and Thunderbird applications. This issue specifically affects versions prior to Firefox 3.6.24 and Thunderbird 3.1.6, where the JSSubScriptLoader component fails to properly manage XPCNativeWrappers during sub-script loading operations. The flaw stems from inadequate handling of the unwrapping process that occurs when add-ons attempt to load external JavaScript resources through the loadSubScript method, creating a pathway for malicious actors to exploit the underlying security boundaries.
The technical implementation of this vulnerability involves the improper management of XPCNativeWrappers, which are JavaScript objects that provide access to native C++ objects within the Firefox runtime environment. When the loadSubScript method is invoked within an add-on context, the JSSubScriptLoader component does not sufficiently validate or sanitize the unwrapping behavior of these native wrappers. This oversight allows attackers to craft malicious web pages that can manipulate the unwrapping process to bypass security restrictions. The vulnerability is particularly concerning because it leverages existing add-on functionality to create a privilege escalation vector, making it more difficult to detect and prevent through standard security measures.
The operational impact of CVE-2011-3647 extends beyond simple script execution, as it enables attackers to gain elevated privileges within the browser environment. This privilege escalation capability means that a remote attacker could potentially execute arbitrary code with the same privileges as the browser process itself. The vulnerability's relationship to CVE-2011-3004 demonstrates a pattern of similar issues within Firefox's security architecture, indicating broader systemic problems in how the application handles native wrapper management. Attackers can exploit this weakness by crafting malicious web content that triggers the vulnerable code path, potentially leading to complete browser compromise and user data exposure.
From a cybersecurity perspective, this vulnerability aligns with CWE-284, which addresses improper access control in software systems, and maps to ATT&CK technique T1059.007 for JavaScript execution within browser environments. The flaw represents a classic example of how seemingly benign functionality can become a security risk when proper boundary checking is omitted. Organizations should prioritize immediate patching of affected versions, as the vulnerability provides attackers with a relatively straightforward path to privilege escalation. Additionally, security teams should implement monitoring for unusual add-on behavior and consider temporary disablement of non-essential add-ons until full patches are deployed. The incident underscores the importance of maintaining strict security boundaries between different execution contexts within browser environments and highlights the need for comprehensive security testing of all JavaScript execution pathways.