CVE-2011-0056 in Firefox
Summary
by MITRE
Buffer overflow in the JavaScript engine in Mozilla Firefox before 3.5.17 and 3.6.x before 3.6.14, and SeaMonkey before 2.0.12, might allow remote attackers to execute arbitrary code via vectors involving exception timing and a large number of string values, aka an "atom map" issue.
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Analysis
by VulDB Data Team • 10/18/2021
The vulnerability identified as CVE-2011-0056 represents a critical buffer overflow flaw within the JavaScript engine of Mozilla Firefox and SeaMonkey browsers. This security issue affects versions prior to Firefox 3.5.17 and 3.6.x before 3.6.14, as well as SeaMonkey before 2.0.12, creating a significant attack surface for remote code execution. The flaw specifically manifests in the atom map implementation, which serves as a critical component in JavaScript engine optimization by caching frequently used string values and identifiers. This particular vulnerability falls under CWE-121, which describes stack-based buffer overflow conditions, and demonstrates the dangerous intersection of memory management and JavaScript engine optimization.
The technical exploitation of this vulnerability occurs through carefully crafted JavaScript code that manipulates exception handling timing while simultaneously processing a large volume of string values. The atom map mechanism maintains a hash table of string atoms used by the JavaScript engine, and when combined with specific timing conditions during exception processing, the buffer overflow can be triggered. Attackers can leverage this flaw by crafting malicious web pages that cause the JavaScript engine to allocate excessive memory within the atom map structure, ultimately leading to memory corruption that can be exploited to execute arbitrary code with the privileges of the affected browser process. This attack vector is particularly insidious because it operates entirely within the browser's JavaScript execution environment without requiring any user interaction beyond visiting a malicious website.
The operational impact of CVE-2011-0056 extends far beyond simple remote code execution, as it provides attackers with complete system compromise capabilities when combined with other exploitation techniques. The vulnerability's presence in widely used browsers such as Firefox and SeaMonkey creates a massive attack surface affecting millions of users globally, making it a prime target for cybercriminals and nation-state actors. The timing-based nature of the exploit means that traditional security measures like web application firewalls may not effectively detect or prevent the attack, as the malicious JavaScript appears legitimate during initial analysis. This vulnerability aligns with ATT&CK technique T1059.007 for JavaScript and with T1203 for Exploitation for Client Execution, demonstrating how browser-based attacks can leverage fundamental engine flaws to achieve complete system compromise.
Mitigation strategies for this vulnerability require immediate patch deployment and system hardening measures that address both the specific buffer overflow condition and broader browser security practices. Organizations should prioritize updating all affected browser versions to their patched releases, as the vulnerability cannot be effectively mitigated through configuration changes alone. The fix implemented by Mozilla involved strengthening memory allocation bounds checking within the atom map implementation and introducing additional safeguards against excessive memory consumption during JavaScript execution. Additional defensive measures include implementing browser sandboxing, restricting JavaScript execution capabilities, and deploying web filtering solutions that can detect and block known malicious JavaScript patterns. The vulnerability also highlights the importance of regular security assessments and continuous monitoring of browser-based attack surfaces, particularly focusing on JavaScript engine components that handle memory management and optimization.