CVE-2008-4324 in Firefox
Summary
by MITRE
The user interface event dispatcher in Mozilla Firefox 3.0.3 on Windows XP SP2 allows remote attackers to cause a denial of service (NULL pointer dereference and application crash) via a series of keypress, click, onkeydown, onkeyup, onmousedown, and onmouseup events. NOTE: it was later reported that Firefox 3.0.2 on Mac OS X 10.5 is also affected.
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Analysis
by VulDB Data Team • 05/25/2025
The vulnerability identified as CVE-2008-4324 represents a critical denial of service weakness in Mozilla Firefox 3.0.3 running on Windows XP Service Pack 2, with additional impacts on Firefox 3.0.2 on Mac OS X 10.5. This flaw resides within the browser's user interface event dispatcher component, which is responsible for managing and processing various user interaction events including keyboard input and mouse operations. The vulnerability specifically manifests when the browser encounters a sequence of carefully crafted events that trigger a NULL pointer dereference condition within the event handling mechanism.
The technical exploitation of this vulnerability occurs through the manipulation of event sequences that include keypress, click, onkeydown, onkeyup, onmousedown, and onmouseup events. When Firefox processes these events in a particular order or combination, the event dispatcher fails to properly validate pointer references, leading to a situation where the application attempts to access a NULL memory location. This NULL pointer dereference causes the browser to crash immediately, resulting in a complete denial of service for the affected user. The vulnerability is particularly concerning because it can be triggered remotely through malicious web content, making it an attractive target for attackers seeking to disrupt user browsing sessions.
From an operational perspective, this vulnerability poses significant risks to end users and organizations relying on Firefox 3.0.3 for web browsing activities. The remote exploitation capability means that attackers can potentially cause service disruption without requiring local system access or user interaction beyond visiting a malicious website. The impact extends beyond simple browser crashes, as it can be leveraged to create persistent denial of service conditions that may require manual browser restarts or system reboots to resolve. This vulnerability aligns with CWE-476, which specifically addresses NULL pointer dereference conditions in software applications, and represents a classic example of how event handling mechanisms can become attack vectors when proper input validation and pointer management are absent.
The attack surface for this vulnerability is broad, as it affects the core browser functionality that handles all user interactions. Security professionals should note that this flaw demonstrates the importance of robust event handling in web browsers, particularly when dealing with complex user interaction sequences that may be manipulated by malicious actors. The vulnerability also relates to ATT&CK technique T1499.004, which covers "Evasion: File and Directory Permissions Modification" through browser-based attacks, as the denial of service can be used to prevent legitimate access to browser functionality. Organizations should implement immediate mitigation strategies including browser updates, network-based filtering of malicious content, and user education about avoiding untrusted websites that may contain exploit code designed to trigger this specific vulnerability pattern.
Mitigation efforts should prioritize immediate patching of affected Firefox versions to address the underlying event dispatcher flaw. System administrators should also consider implementing additional security controls such as browser sandboxing mechanisms, content filtering solutions, and network-based intrusion detection systems that can identify and block malicious event sequences. The vulnerability underscores the critical importance of regular security updates and proper input validation in browser applications, particularly in event-driven systems where user interaction can be manipulated to trigger internal application failures. Organizations should also conduct vulnerability assessments to identify other potential event handling weaknesses in their browser environments and implement comprehensive security monitoring to detect exploitation attempts targeting similar vulnerabilities.