CVE-2011-3650 in Firefox
Summary
by MITRE
Mozilla Firefox before 3.6.24 and 4.x through 7.0 and Thunderbird before 3.1.6 and 5.0 through 7.0 do not properly handle JavaScript files that contain many functions, which allows user-assisted remote attackers to cause a denial of service (memory corruption and application crash) or possibly have unspecified other impact via a crafted file that is accessed by debugging APIs, as demonstrated by Firebug.
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Analysis
by VulDB Data Team • 11/26/2021
This vulnerability affects Mozilla Firefox versions prior to 3.6.24 and 4.x through 7.0, as well as Thunderbird versions before 3.1.6 and 5.0 through 7.0, representing a critical memory corruption issue that stems from improper handling of JavaScript files containing excessive functions. The flaw manifests when debugging APIs encounter crafted JavaScript files with an unusually high number of functions, leading to unpredictable behavior that can result in application crashes or more severe consequences. The vulnerability was demonstrated through Firebug, a popular web development tool, highlighting the risk to developers and end users who rely on debugging functionality for web application analysis. This issue falls under CWE-129, which addresses improper validation of array indices, and represents a classic buffer overflow scenario where memory allocation becomes corrupted due to excessive function declarations in JavaScript code. The vulnerability operates at the intersection of JavaScript engine execution and debugging API interaction, creating a pathway for attackers to exploit memory management weaknesses in the browser's JavaScript runtime environment.
The technical implementation of this vulnerability involves the JavaScript engine's handling of function declarations within script files, where the parser fails to properly validate or limit the number of functions that can be processed during debugging operations. When a maliciously crafted JavaScript file containing thousands or tens of thousands of function declarations is loaded and accessed through debugging APIs, the browser's memory management system becomes overwhelmed, leading to heap corruption or stack overflow conditions. The memory corruption occurs because the JavaScript engine's internal data structures for function management do not adequately enforce reasonable limits on function count, allowing an attacker to exhaust memory resources or manipulate memory pointers in ways that cause the application to crash or behave unpredictably. This vulnerability is particularly dangerous because it requires user interaction to trigger, as the malicious file must be accessed through debugging APIs, making it a user-assisted remote attack vector. The attack scenario typically involves a user opening a web page containing the malicious JavaScript or loading a file through a debugging tool, which then processes the excessive function count and triggers the memory corruption.
The operational impact of CVE-2011-3650 extends beyond simple denial of service, as the memory corruption can potentially lead to arbitrary code execution or information disclosure depending on the specific memory layout and exploitation conditions. Attackers can leverage this vulnerability to crash browser processes, forcing users to restart applications and disrupting normal workflow, while more sophisticated exploitation attempts could potentially allow for privilege escalation or data compromise. The vulnerability affects both Firefox and Thunderbird, broadening its potential impact across email clients and web browsers, making it particularly concerning for enterprise environments where these applications are widely deployed. From an att&ck framework perspective, this vulnerability maps to the T1059.007 technique for 'Command and Scripting Interpreter: JavaScript' and the T1499.004 technique for 'Toggle File Execution' as it involves manipulation of JavaScript execution contexts to achieve system-level impacts. The vulnerability also relates to T1566.001 for 'Phishing: Spearphishing Attachment' since attackers could deliver malicious JavaScript files through email attachments or web pages, and T1068 for 'Exploitation for Privilege Escalation' when the memory corruption leads to more severe system compromise.
Mitigation strategies for this vulnerability include immediate patching of affected browser versions, as Mozilla released security updates addressing the specific memory handling issues in Firefox 3.6.24 and 4.x through 7.0, as well as Thunderbird 3.1.6 and 5.0 through 7.0. Organizations should implement strict content filtering policies to prevent users from accessing untrusted JavaScript files, particularly those that may contain excessive function declarations or appear suspicious. Browser security configurations should be hardened by disabling unnecessary debugging APIs or restricting their access to trusted sources only, while implementing sandboxing techniques to limit the potential impact of any successful exploitation attempts. Additionally, security monitoring should be enhanced to detect unusual JavaScript execution patterns or memory usage spikes that might indicate exploitation attempts. The vulnerability serves as a reminder of the importance of proper input validation and resource limiting in JavaScript engines, as well as the need for comprehensive security testing of debugging and development tools that interface with application execution environments. Network administrators should also consider implementing web application firewalls or content security policies that can detect and block malicious JavaScript patterns, particularly those with excessive function declarations or other anomalous code structures that could trigger similar memory corruption vulnerabilities.