CVE-2011-0066 in Firefox
Summary
by MITRE
Use-after-free vulnerability in Mozilla Firefox before 3.5.19 and 3.6.x before 3.6.17, and SeaMonkey before 2.0.14, allows remote attackers to execute arbitrary code via vectors related to OBJECT s mObserverList.
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Analysis
by VulDB Data Team • 11/06/2021
The CVE-2011-0066 vulnerability represents a critical use-after-free flaw affecting Mozilla Firefox versions prior to 3.5.19 and 3.6.x before 3.6.17, along with SeaMonkey versions before 2.0.14. This vulnerability resides in the browser's handling of OBJECT elements and specifically involves the mObserverList member variable, which creates a dangerous condition where memory previously freed is accessed by subsequent operations. The flaw manifests when the browser processes web content containing malicious OBJECT elements that trigger improper memory management during the observer list cleanup process. This vulnerability falls under the CWE-416 category of Use After Free, which is classified as a serious memory safety issue that can lead to arbitrary code execution.
The technical exploitation of this vulnerability occurs when malicious web content triggers the creation and subsequent destruction of OBJECT elements within the browser's rendering engine. During the cleanup phase, the mObserverList member variable contains references to objects that have already been freed from memory, creating a situation where an attacker can manipulate the memory layout to redirect execution flow. The vulnerability exploits the browser's failure to properly validate observer list references after memory deallocation, allowing attackers to write data to freed memory locations and potentially overwrite function pointers or other critical data structures. This type of memory corruption vulnerability is particularly dangerous because it can be leveraged to execute arbitrary code with the privileges of the browser process.
The operational impact of CVE-2011-0066 is severe and affects a broad range of users who rely on affected browser versions. Attackers can craft malicious web pages that, when visited by users, trigger the vulnerable code path and execute arbitrary commands on the victim's system. This vulnerability can be exploited in the context of a web browser to perform privilege escalation, install malware, steal sensitive information, or establish persistent backdoors. The attack vector requires only a user visiting a malicious website, making it particularly dangerous for phishing campaigns and drive-by download attacks. The vulnerability demonstrates the critical importance of proper memory management in browser engines and highlights the risks associated with complex web content processing systems.
Mitigation strategies for this vulnerability include immediate deployment of security patches provided by Mozilla, which address the memory management issues in the OBJECT element handling code. Organizations should implement comprehensive patch management procedures to ensure all affected browser installations are updated promptly. Browser security configurations should include disabling unnecessary plugins and restricting access to potentially malicious content through content filtering systems. Network-level protections such as web application firewalls and intrusion prevention systems can help detect and block exploitation attempts. Additionally, users should be educated about the risks of visiting untrusted websites and the importance of keeping browser software updated. This vulnerability aligns with ATT&CK technique T1203 for Exploitation for Client Execution and demonstrates the ongoing need for robust memory safety practices in web browser development. The incident underscores the critical relationship between software quality assurance and security vulnerability management in preventing successful exploitation attempts.