CVE-2017-5385 in Firefox
Summary
by MITRE
Data sent with in multipart channels, such as the multipart/x-mixed-replace MIME type, will ignore the referrer-policy response header, leading to potential information disclosure for sites using this header. This vulnerability affects Firefox < 51.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 08/02/2020
This vulnerability resides in the Firefox web browser's handling of multipart content types, specifically the multipart/x-mixed-replace MIME type which is commonly used for streaming content such as live video feeds or dynamic web pages. The flaw occurs when browsers process multipart responses where the referrer-policy header is present in the HTTP response but is ignored during the processing of these specific multipart channels. This represents a critical information disclosure vulnerability as it allows malicious actors to bypass intended referrer policy protections that are designed to prevent sensitive information from being leaked through referrer headers when navigating between different origins.
The technical implementation of this vulnerability stems from Firefox's inconsistent handling of referrer policies across different content types. When a web server sends a response with a referrer-policy header, browsers should respect this directive to control how referrer information is transmitted when users navigate from one page to another. However, Firefox version 51 and earlier failed to apply these policies consistently when processing multipart content, particularly the multipart/x-mixed-replace type which is often used for continuous data streams. This inconsistency creates a pathway for attackers to extract referrer information that would normally be protected by the policy, potentially exposing sensitive data from authenticated sessions or private communications.
The operational impact of this vulnerability extends beyond simple information disclosure, as it undermines fundamental web security principles that users expect from modern browsers. Attackers can exploit this flaw by crafting malicious multipart responses that, when processed by vulnerable Firefox versions, can leak referrer information to third-party domains. This could result in the exposure of sensitive session identifiers, user authentication tokens, or other confidential data that should remain protected by the referrer policy. The vulnerability affects not only individual users but also organizations that rely on referrer policies as part of their security posture, potentially compromising the integrity of cross-origin navigation protections. Security researchers have classified this as a medium to high severity issue due to its potential for exploitation in real-world scenarios.
Organizations and users should immediately update to Firefox version 51 or later, where this vulnerability has been addressed through proper implementation of referrer policy enforcement across all content types. The fix involves ensuring that multipart response headers are processed with the same referrer policy consistency as other HTTP responses, preventing the bypass of security controls that are critical for maintaining user privacy and data protection. System administrators should also monitor for potential exploitation attempts in their network traffic logs, particularly looking for unusual multipart content requests that might indicate attempts to leverage this vulnerability. This issue aligns with CWE-200, which covers "Information Exposure," and can be mapped to ATT&CK technique T1071.004 for application layer protocol manipulation, demonstrating how seemingly minor implementation gaps in browser security can create significant attack vectors that require immediate remediation.