CVE-2008-1238 in Firefox
Summary
by MITRE
Mozilla Firefox before 2.0.0.13 and SeaMonkey before 1.1.9, when generating the HTTP Referer header, does not list the entire URL when it contains Basic Authentication credentials without a username, which makes it easier for remote attackers to bypass application protection mechanisms that rely on Referer headers, such as with some Cross-Site Request Forgery (CSRF) mechanisms.
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Analysis
by VulDB Data Team • 08/07/2019
This vulnerability affects web browsers that implement HTTP Referer header generation, specifically Mozilla Firefox versions prior to 2.0.0.13 and SeaMonkey versions prior to 1.1.9. The flaw stems from how these browsers handle URLs containing Basic Authentication credentials when constructing Referer headers for HTTP requests. When a URL includes Basic Authentication information without a username component, the browser fails to properly encode or transmit the complete URL within the Referer header field. This behavior creates a security gap that can be exploited by malicious actors to circumvent protection mechanisms relying on Referer header validation.
The technical implementation issue manifests when browsers process URLs with Basic Authentication credentials that lack explicit usernames. In such cases, the browser's HTTP Referer header generation logic does not correctly handle the URL encoding, resulting in truncated or malformed Referer values. This occurs because the authentication component of the URL, particularly when username is absent, gets processed in a way that omits parts of the original URL during header construction. The vulnerability is categorized under CWE-200, which deals with Information Exposure Through Sent Data, and represents a specific implementation flaw in HTTP header generation.
The operational impact of this vulnerability extends beyond simple information disclosure, as it directly undermines security mechanisms that depend on Referer header validation for protection. Many web applications implement CSRF protection by checking the Referer header to verify that requests originate from legitimate sources within the same domain. When the Referer header contains incomplete URL information due to this flaw, attackers can craft requests that appear to come from trusted sources, thereby bypassing these security controls. This weakness can be particularly dangerous in applications that rely heavily on Referer-based validation for access control decisions, potentially allowing unauthorized actions to be performed on behalf of authenticated users.
Attackers can exploit this vulnerability by constructing malicious URLs that contain Basic Authentication credentials without usernames, then using these URLs to trigger requests where the truncated Referer header will not match the expected domain or path. This creates opportunities for CSRF attacks where the application's Referer-based validation fails to detect that the request is being made from an external source. The vulnerability aligns with ATT&CK technique T1566.001, which covers Social Engineering through Spearphishing Attachments, as attackers can leverage this weakness to craft more effective phishing attacks that bypass security controls relying on Referer validation. Organizations should implement additional CSRF protection mechanisms beyond Referer header validation, such as implementing anti-CSRF tokens, using SameSite cookies, or employing additional request validation techniques to mitigate the risk of exploitation.
The flaw demonstrates a critical oversight in HTTP protocol implementation within web browsers, particularly in how they handle URL parsing and header construction for authentication contexts. This vulnerability underscores the importance of proper URL encoding and validation in security-sensitive contexts, as even seemingly minor implementation details in browser behavior can have significant security implications. The issue highlights the need for comprehensive testing of HTTP header generation logic, especially in authentication-related scenarios where incomplete or malformed headers could be exploited to bypass security controls. Organizations should ensure their browsers are updated to versions that properly handle Basic Authentication credentials in Referer headers and implement layered security approaches to protect against potential exploitation of such weaknesses.