CVE-2010-1121 in Firefox
Summary
by MITRE
Mozilla Firefox 3.6.x before 3.6.3 does not properly manage the scopes of DOM nodes that are moved from one document to another, which allows remote attackers to conduct use-after-free attacks and execute arbitrary code via unspecified vectors involving improper interaction with garbage collection, as demonstrated by Nils during a Pwn2Own competition at CanSecWest 2010.
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Analysis
by VulDB Data Team • 05/03/2026
The vulnerability identified as CVE-2010-1121 represents a critical memory safety issue within Mozilla Firefox versions 3.6.x prior to 3.6.3, specifically targeting the browser's handling of Document Object Model node management during document transitions. This flaw stems from inadequate scope management when DOM nodes are transferred between different document contexts, creating a scenario where memory locations may be prematurely freed while still being referenced by active code paths. The vulnerability was particularly significant because it was demonstrated in a real-world attack scenario during the Pwn2Own competition at CanSecWest 2010, where security researcher Nils successfully exploited the flaw to achieve remote code execution. The technical implementation involves improper interaction with the browser's garbage collection mechanism, where the system fails to properly track references to DOM nodes that have been moved between documents, leading to potential use-after-free conditions that can be leveraged by malicious actors.
The operational impact of this vulnerability extends beyond simple browser exploitation to encompass broader security implications for web application environments and user systems. When DOM nodes are moved between documents without proper reference tracking, the garbage collector may prematurely deallocate memory that is still referenced by scripts or DOM handlers, creating opportunities for attackers to manipulate memory contents through carefully crafted web content. This type of vulnerability falls under the CWE-416 category of Use After Free conditions, which are particularly dangerous because they can lead to arbitrary code execution when attackers can control the memory layout and overwrite critical function pointers or code segments. The exploitation technique relies on the attacker's ability to manipulate DOM node lifecycles and trigger garbage collection at specific moments to achieve the desired memory corruption state.
The security implications of CVE-2010-1121 align with several ATT&CK framework techniques, particularly those related to privilege escalation and code execution through memory corruption vulnerabilities. The attack vector demonstrates how improper memory management in web browsers can be leveraged to bypass security boundaries and execute malicious code with the privileges of the browser process. This vulnerability represents a classic example of how browser security models can be undermined through subtle memory management flaws, as the exploitation requires precise timing and understanding of the browser's internal memory management systems. The fact that this vulnerability was demonstrated at a major security conference underscores its practical exploitability and the significant risk it posed to users of affected Firefox versions. Organizations and users were particularly vulnerable because the attack could be executed through standard web browsing activities without requiring any special user interaction beyond visiting a malicious website, making it a particularly concerning security flaw in the context of web browser security. The vulnerability required immediate patching and highlighted the importance of proper memory management in complex web applications, as the flaw existed in the core browser engine that handles all web content processing.