CVE-2006-2332 in Firefox
Summary
by MITRE
Mozilla Firefox 1.5.0.3 allows remote attackers to cause a denial of service via a web page with a large number of IMG elements in which the SRC attribute is a mailto URI. NOTE: another researcher found that the web page caused a temporary browser slowdown instead of a crash.
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Analysis
by VulDB Data Team • 07/26/2018
This vulnerability affects Mozilla Firefox version 1.5.0.3 and represents a denial of service weakness that can be exploited through carefully crafted web content. The flaw manifests when a web page contains an excessive number of img elements where each element references a mailto URI in its src attribute. This specific attack vector leverages the browser's handling of email links within image tags to create resource exhaustion conditions. The vulnerability operates by triggering Firefox's internal processing of mailto URIs in image contexts, causing the browser to attempt to handle numerous email link requests simultaneously. The original report indicated potential for complete browser crashes, though subsequent research revealed the more common outcome was temporary browser slowdown rather than complete system failure. This behavior demonstrates how seemingly benign HTML elements can be weaponized to consume system resources and degrade user experience.
The technical implementation of this vulnerability stems from Firefox's inadequate handling of malformed or excessive mailto URI references within image tags. When the browser encounters multiple img elements with mailto: protocol in their src attributes, it attempts to process each reference as if it were a legitimate email address. This processing involves various internal mechanisms including URI parsing, email client detection, and potentially network connection attempts. The vulnerability exists because Firefox does not properly limit or throttle the number of concurrent mailto URI processing operations, nor does it implement adequate resource management when encountering excessive image elements. This weakness aligns with CWE-400, which covers unspecified resource management issues, and specifically demonstrates how improper input validation can lead to resource exhaustion attacks. The vulnerability operates at the application layer and represents a classic example of how web browsers can be made to consume excessive memory or CPU cycles through malformed content.
The operational impact of this vulnerability extends beyond simple browser performance degradation to potentially affect user productivity and system availability. When exploited, the vulnerability can cause Firefox to become unresponsive for extended periods, forcing users to manually terminate the browser process or restart their systems. This type of denial of service attack can be particularly problematic in environments where multiple users rely on browser-based applications or where automated systems depend on consistent browser behavior. The attack requires minimal technical expertise to execute, making it accessible to casual attackers who simply need to create a web page with the specific structure. From an attacker's perspective, this vulnerability provides a reliable method for disrupting user sessions and can be easily automated. The temporary nature of the slowdown means that while immediate system crashes are less likely, sustained exploitation can create ongoing disruption and user frustration.
Mitigation strategies for this vulnerability should focus on both immediate defensive measures and long-term architectural improvements. Users should immediately update to Firefox versions that contain patches addressing this specific weakness, as version 1.5.0.4 and later included fixes for the mailto URI processing issue. Browser vendors should implement stricter limits on the number of concurrent URI processing operations and introduce more robust input validation for image source attributes. Network administrators can deploy content filtering solutions that identify and block web pages containing excessive img elements with mailto URIs. Additionally, implementing browser security policies that limit the execution of potentially malicious content can provide layered protection. The vulnerability highlights the importance of proper resource management in web browsers and demonstrates why security updates should be applied promptly. Organizations should consider implementing automated patch management systems to ensure all browser installations remain current with security fixes, as this type of vulnerability can remain exploitable for extended periods if not properly addressed.