CVE-2011-0085 in Firefox
Summary
by MITRE
Use-after-free vulnerability in the nsXULCommandDispatcher function in Mozilla Firefox before 3.6.18, Thunderbird before 3.1.11, and SeaMonkey through 2.0.14 allows remote attackers to execute arbitrary code via a crafted XUL document that dequeues the current command updater.
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Analysis
by VulDB Data Team • 11/13/2021
The CVE-2011-0085 vulnerability represents a critical use-after-free flaw in Mozilla's XUL command dispatcher mechanism that affected multiple browser and email client applications. This vulnerability resides within the nsXULCommandDispatcher function which manages command execution and updates within the Mozilla application framework. The flaw manifests when processing crafted XUL documents that manipulate the command updater queue, creating a scenario where freed memory locations are accessed after being deallocated. This type of vulnerability falls under the CWE-416 category, specifically addressing use-after-free conditions that occur when memory is accessed after it has been freed by a program. The vulnerability affects Firefox versions prior to 3.6.18, Thunderbird versions prior to 3.1.11, and SeaMonkey versions through 2.0.14, indicating a widespread impact across the Mozilla ecosystem.
The technical exploitation of this vulnerability occurs through the manipulation of XUL (XML User Interface Language) documents, which are used by Mozilla applications to define user interfaces and command handling. When a malicious XUL document is processed, it can cause the command dispatcher to dequeue a command updater that has already been freed from memory. This memory management error creates a situation where subsequent operations attempt to access memory that has been reallocated or deallocated, potentially allowing attackers to execute arbitrary code with the privileges of the affected application. The attack vector is particularly insidious because it requires only the delivery of a crafted XUL document, which can be embedded in web pages or email messages, making it a potent remote code execution vulnerability. The vulnerability demonstrates characteristics consistent with the attack pattern described in the MITRE ATT&CK framework under the T1059.007 technique for command and scripting interpreter, as it enables arbitrary code execution through manipulation of the application's command processing mechanisms.
The operational impact of CVE-2011-0085 is severe, as it provides remote attackers with the ability to execute arbitrary code on vulnerable systems without requiring user interaction beyond visiting a malicious website or opening a compromised email message. This makes the vulnerability particularly dangerous in phishing attacks or drive-by download scenarios where attackers can leverage the use-after-free condition to gain complete control over affected systems. The vulnerability's widespread impact across multiple Mozilla applications means that organizations using Firefox, Thunderbird, or SeaMonkey were all at risk, requiring coordinated patching efforts across different software products. The memory corruption aspect of this vulnerability also makes it susceptible to exploitation techniques involving heap spraying or return-oriented programming, further increasing the potential for successful attacks. Security researchers have noted that such use-after-free vulnerabilities often serve as the foundation for more sophisticated attacks, as they can be combined with other techniques to bypass modern exploit mitigations like address space layout randomization and data execution prevention mechanisms. The vulnerability highlights the importance of proper memory management in complex application frameworks and underscores the need for comprehensive code review processes that identify potential race conditions and improper memory handling patterns. Organizations affected by this vulnerability needed to implement immediate patch management procedures and consider network-based mitigations such as web application firewalls to protect against exploitation attempts while waiting for official security updates to be deployed across their systems.