CVE-2015-4483 in Firefox
Summary
by MITRE
Mozilla Firefox before 40.0 allows man-in-the-middle attackers to bypass a mixed-content protection mechanism via a feed: URL in a POST request.
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Analysis
by VulDB Data Team • 06/09/2022
The vulnerability identified as CVE-2015-4483 represents a critical flaw in Mozilla Firefox's mixed-content protection mechanisms that persisted through versions prior to 40.0. This security weakness specifically targets the browser's handling of feed: URLs within POST requests, creating an avenue for man-in-the-middle attackers to circumvent essential security protections designed to prevent the loading of insecure content alongside secure web pages. The flaw essentially undermines Firefox's ability to properly identify and block mixed content scenarios where potentially malicious actors could exploit the inconsistent URL handling to inject harmful resources into otherwise secure contexts.
The technical root cause of this vulnerability lies in Firefox's insufficient validation of feed: URLs when processing POST requests, which allows attackers to manipulate how the browser interprets and processes content delivery mechanisms. This improper handling creates a scenario where the mixed-content blocking system fails to properly recognize when a feed URL might be attempting to load insecure resources, particularly when these URLs are embedded within POST request payloads. The vulnerability specifically exploits the gap between how Firefox processes different URL schemes and how it applies security policies to content loaded through various request methods, particularly when feed protocols are involved in POST operations.
The operational impact of this vulnerability extends beyond simple security bypass to potentially enable attackers to execute sophisticated man-in-the-middle attacks that could compromise user data and system integrity. When an attacker successfully exploits this weakness, they can force the browser to load insecure content from untrusted sources while maintaining the appearance of secure communication, effectively neutralizing the mixed-content protection that users expect from modern browsers. This vulnerability particularly affects scenarios where users interact with web applications that utilize feed protocols or content delivery systems that might be vulnerable to POST-based manipulation, creating opportunities for attackers to inject malicious scripts, redirect users to phishing sites, or otherwise compromise the security assurances that secure browsing environments should provide.
This vulnerability aligns with CWE-310, which addresses cryptographic weaknesses in protocol implementations, and represents a specific instance where the security controls designed to protect against mixed-content attacks were insufficiently applied to certain URL schemes. The flaw demonstrates how protocol-specific handling can create security gaps when different content delivery mechanisms are not uniformly protected by the same security policies. From an ATT&CK framework perspective, this vulnerability maps to techniques involving credential access and execution of malicious code through web-based attacks, specifically leveraging the browser's trust model to bypass security boundaries. Organizations and users affected by this vulnerability should immediately update to Firefox version 40.0 or later, where the mixed-content protection mechanisms have been properly enhanced to address this specific class of attack vectors. Additionally, security teams should implement network monitoring to detect unusual POST request patterns involving feed URLs and consider implementing additional layers of content filtering to mitigate potential exploitation attempts.