CVE-2010-0168 in Firefox
Summary
by MITRE
The nsDocument::MaybePreLoadImage function in content/base/src/nsDocument.cpp in the image-preloading implementation in Mozilla Firefox 3.6 before 3.6.2 does not apply scheme restrictions and policy restrictions to the image's URL, which might allow remote attackers to cause a denial of service (application crash or hang) or hijack the functionality of the browser's add-ons via a crafted SRC attribute of an IMG element, as demonstrated by remote command execution through an ssh: URL in a configuration that supports gnome-vfs with a nonstandard network.gnomevfs.supported-protocols setting.
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Analysis
by VulDB Data Team • 05/03/2026
The vulnerability described in CVE-2010-0168 represents a critical security flaw in Mozilla Firefox 3.6 versions prior to 3.6.2 that stems from inadequate URL validation within the image preloading mechanism. This issue resides in the nsDocument::MaybePreLoadImage function located in content/base/src/nsDocument.cpp, where the implementation fails to properly enforce scheme restrictions and policy restrictions on image URLs. The flaw allows remote attackers to manipulate the browser's image loading behavior through crafted SRC attributes in IMG elements, creating a vector for both denial of service and potential functionality hijacking.
The technical implementation of this vulnerability exploits the absence of proper URL validation during the image preloading process, which occurs before the browser has fully processed the security context of the requested resource. When Firefox attempts to preload images, it does not adequately filter URLs based on their scheme or apply appropriate policy restrictions that would normally prevent potentially malicious URLs from being processed. This oversight creates an environment where attackers can specify URLs with schemes that should normally be restricted, such as ssh: URLs, which can trigger unexpected behavior in the browser's underlying network subsystem.
The operational impact of this vulnerability extends beyond simple denial of service to include potential remote code execution capabilities when specific system configurations are present. The vulnerability demonstrates particular risk when Firefox is configured with gnome-vfs support and has nonstandard network.gnomevfs.supported-protocols settings, allowing attackers to leverage the browser's integration with the gnome-vfs subsystem to execute commands remotely. This represents a sophisticated attack vector that combines browser exploitation with system-level integration, potentially enabling attackers to bypass traditional web security boundaries and gain unauthorized access to system resources.
The security implications align with CWE-20, which addresses "Improper Input Validation," and represents a classic case of insufficient restrictions on URL schemes and protocols. From an attack framework perspective, this vulnerability maps to ATT&CK technique T1059.007 for remote command execution and T1498 for denial of service, while also supporting T1190 through the exploitation of browser vulnerabilities. The vulnerability's exploitation requires minimal user interaction beyond visiting a malicious webpage, making it particularly dangerous in phishing scenarios or when combined with other attack vectors.
Mitigation strategies for this vulnerability include immediate upgrading to Firefox 3.6.2 or later versions where the patch has been implemented, as well as implementing network-level restrictions that prevent access to potentially dangerous URL schemes. Organizations should also consider disabling unnecessary browser integration features such as gnome-vfs support when not required, and implementing strict content security policies that limit the types of URLs that can be loaded within browser contexts. Additionally, regular security audits of browser configurations and monitoring for suspicious URL patterns can help detect potential exploitation attempts before they succeed.