CVE-2009-2478 in Firefox
Summary
by MITRE
Mozilla Firefox 3.5 allows remote attackers to cause a denial of service (NULL pointer dereference and application crash) via unspecified vectors, related to a "flash bug."
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Analysis
by VulDB Data Team • 11/16/2025
The vulnerability identified as CVE-2009-2478 represents a critical denial of service flaw affecting Mozilla Firefox version 3.5 that stems from an unspecified vector related to a flash bug. This issue manifests as a NULL pointer dereference condition that leads to application crashes, effectively disrupting user access to the browser and potentially enabling attackers to exploit this weakness for more sophisticated attacks. The vulnerability's classification as a flash-related bug suggests it involves interactions between Firefox's rendering engine and Adobe Flash content, which was a common attack surface during this period of browser development.
The technical implementation of this vulnerability involves a NULL pointer dereference scenario where Firefox's handling of certain Flash content triggers an invalid memory access pattern. When the browser encounters malformed or malicious Flash objects, the execution flow attempts to dereference a null pointer, causing the application to crash immediately. This type of vulnerability falls under CWE-476 which specifically addresses NULL pointer dereference conditions, representing a fundamental programming error where developers fail to validate pointer values before using them. The flaw exists within Firefox's Flash plugin integration layer, where the browser's JavaScript engine interacts with Flash's ActionScript runtime environment.
From an operational impact perspective, this vulnerability presents significant risks to both individual users and enterprise environments. Attackers can remotely trigger the denial of service condition by delivering malicious web pages containing compromised Flash content, leading to unexpected browser crashes that interrupt user sessions and potentially expose system resources to further exploitation. The vulnerability's remote nature means that users can be compromised simply by visiting malicious websites without any additional user interaction required, making it particularly dangerous in phishing campaigns or exploit kits. This weakness directly impacts the availability and reliability of the Firefox browser, creating opportunities for attackers to perform persistent disruption attacks or use the crash as a stepping stone for more advanced exploitation techniques.
The mitigation strategies for CVE-2009-2478 primarily focus on immediate patch deployment and browser configuration adjustments. Mozilla released Firefox 3.5.1 and subsequent versions that addressed this vulnerability through code modifications in the Flash plugin handling components. Organizations should implement immediate patch management protocols to ensure all affected systems receive the security updates. Additional protective measures include disabling Flash plugin execution in browsers, implementing content filtering solutions, and deploying web application firewalls that can detect and block malicious Flash content. From an ATT&CK framework perspective, this vulnerability relates to techniques involving privilege escalation and denial of service, potentially enabling attackers to progress through the kill chain by first establishing a foothold through browser exploitation before moving toward more sophisticated attacks. The vulnerability also demonstrates the importance of maintaining up-to-date browser security patches and implementing defense-in-depth strategies that reduce the attack surface available to threat actors targeting web browsers.