CVE-2010-0176 in Firefox
Summary
by MITRE
Mozilla Firefox before 3.0.19, 3.5.x before 3.5.9, and 3.6.x before 3.6.2; Thunderbird before 3.0.4; and SeaMonkey before 2.0.4 do not properly manage reference counts for option elements in a XUL tree optgroup, which might allow remote attackers to execute arbitrary code via unspecified vectors that trigger access to deleted elements, related to a "dangling pointer vulnerability."
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Analysis
by VulDB Data Team • 05/05/2026
This vulnerability represents a critical memory safety issue affecting multiple Mozilla applications including Firefox, Thunderbird, and SeaMonkey. The flaw resides in the XUL (XML User Interface Language) tree implementation where option elements within optgroup containers are not properly managing reference counts during object lifecycle operations. This improper reference counting mechanism creates a scenario where objects can be prematurely deallocated while still being referenced elsewhere in the application's memory space.
The technical exploitation of this vulnerability occurs through a dangling pointer condition that arises when the application attempts to access memory locations that have already been freed. When option elements in XUL tree optgroup structures are removed from their parent containers, the reference counting system fails to properly decrement the object's reference count, allowing the object to remain in memory even after it should have been destroyed. Attackers can leverage this condition to craft malicious web content that triggers the creation and subsequent deletion of option elements within XUL tree structures, ultimately leading to memory corruption that can be exploited to execute arbitrary code remotely.
The operational impact of this vulnerability extends across a broad range of affected software versions, creating significant security risks for users of these applications. The vulnerability affects Firefox versions prior to 3.0.19, 3.5.x versions before 3.5.9, and 3.6.x versions before 3.6.2, along with Thunderbird versions before 3.0.4 and SeaMonkey versions before 2.0.4. This widespread impact means that numerous users would be potentially exposed to remote code execution attacks through web browsing or email operations. The vulnerability's classification as a dangling pointer issue aligns with CWE-416, which specifically addresses use after free conditions in software implementations.
The attack vector for this vulnerability typically involves crafting malicious web pages or email content that contains specially constructed XUL tree optgroup elements designed to trigger the reference counting failure. When users navigate to these malicious pages or open affected email messages, the browser or email client processes the XUL structures and inadvertently accesses freed memory locations, potentially allowing attackers to execute malicious code with the privileges of the affected application. This type of exploitation falls under the ATT&CK framework's technique T1059 for executing malicious code, specifically targeting browser-based attack surfaces.
Mitigation strategies for this vulnerability require immediate application of security patches released by Mozilla, which address the reference counting implementation in XUL tree components. System administrators should prioritize deployment of updates across all affected versions of Firefox, Thunderbird, and SeaMonkey to prevent exploitation. Additionally, organizations should implement browser hardening measures including disabling potentially dangerous XUL features when possible, and employing content filtering solutions to block access to known malicious domains. The vulnerability demonstrates the critical importance of proper memory management in browser applications and serves as a reminder of how seemingly minor implementation flaws in reference counting systems can result in severe security consequences, particularly when combined with the complex memory management requirements of modern web browsers.