CVE-2008-5822 in Libxul
Summary
by MITRE
Memory leak in Libxul, as used in Mozilla Firefox 3.0.5 and other products, allows remote attackers to cause a denial of service (memory consumption and browser hang) via a long CLASS attribute in an HR element in an HTML document.
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Analysis
by VulDB Data Team • 08/03/2021
The vulnerability identified as CVE-2008-5822 represents a critical memory management flaw within Libxul, the core component that powers Mozilla Firefox and related applications. This memory leak occurs specifically when processing HTML documents containing excessively long CLASS attributes within HR elements, creating a condition that can be exploited remotely to consume system resources and ultimately cause browser instability. The flaw exists in the parsing and handling mechanisms of the XUL (XML User Interface Language) framework that forms the foundation of Firefox's user interface rendering engine, making it particularly dangerous as it affects the fundamental browser operation.
The technical implementation of this vulnerability stems from inadequate memory management during the processing of HTML elements, particularly when encountering malformed CLASS attributes in HR tags. When a remote attacker crafts an HTML document containing an abnormally long CLASS attribute value within an HR element, the Libxul engine fails to properly release allocated memory resources during the parsing process. This results in progressive memory consumption that can eventually exhaust available system resources, leading to browser hangs or complete application crashes. The vulnerability operates at the application layer and requires no special privileges to exploit, making it particularly dangerous in web browsing environments where users may encounter malicious content without awareness.
From an operational impact perspective, this vulnerability creates significant security risks for end users and organizations relying on affected versions of Firefox and related software. The remote exploitation capability means that attackers can craft malicious web pages that, when viewed by unsuspecting users, will gradually consume system memory until the browser becomes unresponsive or crashes entirely. This denial of service condition can be used as part of broader attack campaigns to disrupt user productivity or as a precursor to more sophisticated attacks that exploit the browser's instability. The vulnerability affects not just Firefox 3.0.5 but also other products that utilize the same Libxul framework, extending its potential impact across multiple applications.
Security professionals should note that this vulnerability aligns with CWE-401, which specifically addresses improper management of memory allocation and deallocation, and represents a classic example of resource exhaustion attacks that fall under ATT&CK technique T1499.1. The memory leak pattern demonstrates how seemingly benign HTML attributes can be weaponized to create persistent resource consumption issues that degrade system performance and availability. Organizations should prioritize immediate patching of affected systems and implement network monitoring to detect potential exploitation attempts. Additionally, browser hardening measures including content filtering and sandboxing mechanisms should be deployed to limit the potential impact of such vulnerabilities. The vulnerability underscores the importance of proper memory management in web rendering engines and highlights the need for comprehensive input validation and resource cleanup procedures in browser security architectures.