CVE-2011-2373 in Firefox
Summary
by MITRE
Use-after-free vulnerability in Mozilla Firefox before 3.6.18 and 4.x through 4.0.1, Thunderbird before 3.1.11, and SeaMonkey through 2.0.14, when JavaScript is disabled, allows remote attackers to execute arbitrary code via a crafted XUL document.
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Analysis
by VulDB Data Team • 11/13/2021
This vulnerability represents a critical use-after-free flaw that affects multiple Mozilla products including Firefox, Thunderbird, and SeaMonkey. The issue occurs specifically when JavaScript is disabled in the browser environment, creating a dangerous condition where freed memory locations are accessed after being deallocated. The vulnerability manifests through crafted XUL documents that exploit the memory management system, allowing attackers to manipulate freed memory pointers and execute arbitrary code on vulnerable systems. This type of vulnerability falls under the CWE-416 category for use-after-free conditions, which is a well-known class of memory corruption vulnerabilities that can lead to complete system compromise. The attack vector leverages the XUL (XML User Interface Language) framework that Mozilla products use for building user interfaces, making it particularly dangerous as it can be triggered through web content that appears legitimate to users.
The technical exploitation of this vulnerability requires attackers to craft malicious XUL documents that can trigger the use-after-free condition in the browser's memory management subsystem. When JavaScript is disabled, the normal security protections that would prevent such exploitation are reduced, creating a window where attackers can manipulate the browser's memory state. The flaw occurs during the processing of XUL documents where the application frees memory resources but continues to reference those locations, allowing for memory corruption that can be leveraged for code execution. This vulnerability is particularly insidious because it can be triggered remotely through web pages, making it a prime target for drive-by download attacks. The attack chain typically involves delivering a malicious XUL document through a compromised website or email attachment, where the browser processes the document and triggers the memory corruption leading to arbitrary code execution.
The operational impact of this vulnerability extends beyond simple privilege escalation as it provides attackers with complete control over affected systems. Successful exploitation allows remote attackers to execute arbitrary code with the privileges of the user running the browser, potentially leading to full system compromise, data exfiltration, or establishment of persistent backdoors. The vulnerability affects a wide range of Mozilla products across multiple versions, making it particularly dangerous as it impacts users across different software ecosystems. The fact that it requires JavaScript to be disabled creates a false sense of security for users who may disable JavaScript as a security measure, only to find that this action inadvertently makes them more vulnerable to this specific attack. Organizations using these browsers are at significant risk as the vulnerability can be exploited through various attack vectors including malicious websites, email attachments, or compromised web applications.
Mitigation strategies for this vulnerability require immediate patching of all affected software versions as the primary defense mechanism. Mozilla released updates for Firefox 3.6.18, Firefox 4.x through 4.0.1, Thunderbird 3.1.11, and SeaMonkey 2.0.14 to address this issue. System administrators should ensure all users have updated to patched versions and implement network-level protections such as web application firewalls and content filtering to prevent access to malicious XUL documents. Additional defensive measures include implementing strict browser security policies that disable XUL loading from untrusted sources, using sandboxing technologies to limit the impact of potential exploitation, and monitoring for suspicious network activity that may indicate exploitation attempts. The vulnerability also highlights the importance of following security best practices such as keeping software updated, implementing multi-layered security controls, and conducting regular security assessments to identify and remediate similar vulnerabilities. This case demonstrates the critical importance of proper memory management in software development and the potential consequences of inadequate memory safety measures in widely deployed applications.