CVE-2008-5012 in Firefox
Summary
by MITRE
Mozilla Firefox 2.x before 2.0.0.18, Thunderbird 2.x before 2.0.0.18, and SeaMonkey 1.x before 1.1.13 do not properly change the source URI when processing a canvas element and an HTTP redirect, which allows remote attackers to bypass the same origin policy and access arbitrary images that are not directly accessible to the attacker. NOTE: this issue can be leveraged to enumerate software on the client by performing redirections related to moz-icon.
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Analysis
by VulDB Data Team • 08/20/2019
This vulnerability represents a critical security flaw in Mozilla Firefox, Thunderbird, and SeaMonkey browsers that stems from improper handling of HTTP redirects in canvas element processing. The issue occurs when a web page attempts to draw an image onto a canvas element, and the image source undergoes an HTTP redirect before the actual image is retrieved. The browsers fail to properly update the source URI during this redirect process, creating a bypass of the same origin policy that is fundamental to web security. This policy normally prevents scripts from accessing resources from different domains to protect against cross-site scripting attacks and data theft. The flaw allows attackers to circumvent these protections and access images that would normally be restricted due to their origin, potentially exposing sensitive information or internal resources that should remain isolated.
The technical implementation of this vulnerability involves the browser's canvas API handling mechanism during HTTP redirect scenarios. When processing canvas elements, the browsers maintain an incorrect source URI reference after redirect operations, enabling malicious actors to exploit this behavior to access resources that should be protected by cross-origin restrictions. The vulnerability specifically affects versions where the redirect handling logic does not properly update the security context of the canvas element, allowing for unauthorized data access. This issue is particularly dangerous because it can be used to enumerate software components on the client system through redirection techniques that leverage the moz-icon protocol, which is used internally by Mozilla applications to reference application resources. The attacker can construct malicious web pages that redirect to internal resources and then access them through the canvas element, effectively bypassing the normal security boundaries that separate user-accessible content from internal application resources.
The operational impact of this vulnerability extends beyond simple data access violations, as it provides attackers with a method to perform reconnaissance on client systems. By leveraging the redirect functionality combined with canvas element processing, malicious actors can determine which software components are present on a victim's system, potentially identifying specific versions and configurations of installed applications. This enumeration capability can be used to tailor more sophisticated attacks targeting known vulnerabilities in specific software versions. The vulnerability affects not only the web browsers themselves but also their underlying security models, as it demonstrates a failure in the origin policy enforcement mechanism that is critical to maintaining secure web execution environments. The impact is particularly severe because it operates at the fundamental level of web security architecture, where the same origin policy is one of the core protections against cross-site attacks.
Mitigation strategies for this vulnerability require immediate patching of affected software versions to address the redirect handling logic in canvas element processing. System administrators should ensure that all installations of Firefox, Thunderbird, and SeaMonkey are updated to versions 2.0.0.18 or later for Firefox, 2.0.0.18 for Thunderbird, and 1.1.13 for SeaMonkey, where the security flaw has been corrected. Organizations should implement comprehensive monitoring for any attempts to exploit this vulnerability through malicious web content and consider network-level controls to restrict access to potentially harmful redirect patterns. The fix involves proper URI handling during HTTP redirect operations, ensuring that the security context of canvas elements is maintained correctly throughout the redirect process. This vulnerability aligns with CWE-200, which addresses information exposure through improper handling of redirects, and can be categorized under ATT&CK technique T1056.001 for input validation and T1566.001 for malicious file execution through web-based attacks. Organizations should also consider implementing additional security measures such as content security policies and web application firewalls to provide defense-in-depth against similar redirect-based attacks that could exploit other components of the web security model.