CVE-2004-0866 in Internet Explorer
Summary
by MITRE
Internet Explorer 6.0 allows web sites to set cookies for country-specific top-level domains, such as .ltd.uk, .plc.uk, and .sch.uk, which could allow remote attackers to perform a session fixation attack and hijack a user s HTTP session.
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Analysis
by VulDB Data Team • 06/30/2021
This vulnerability in Internet Explorer 6.0 represents a significant session security flaw that exploits the browser's cookie handling mechanism for country-specific top-level domains. The issue arises from the browser's improper validation of cookie domain attributes when dealing with complex domain structures such as .ltd.uk, .plc.uk, and .sch.uk which are legitimate United Kingdom domain extensions. When a malicious web site sets a cookie with a domain attribute that matches these country-specific TLDs, the browser incorrectly processes the cookie domain validation, allowing attackers to set cookies that can be used to hijack user sessions across different subdomains.
The technical implementation of this vulnerability stems from IE6.0's overly permissive cookie domain validation logic that fails to properly enforce the standard cookie security model. According to the cookie specification and CWE-384, this represents a weakness in session management where the browser does not adequately validate domain attributes to prevent cross-domain cookie contamination. The flaw specifically manifests when the browser's cookie parsing engine does not correctly identify the effective domain for cookies set on these complex UK domain extensions, leading to improper cookie scope enforcement. This behavior violates the principle of least privilege in session management and creates an attack vector where malicious actors can set cookies that persist across different subdomains within the same country-specific domain structure.
The operational impact of this vulnerability is severe as it enables session fixation attacks where attackers can establish a known session identifier and then trick users into using that identifier, effectively allowing the attacker to hijack user sessions. This attack vector is particularly dangerous because it can be exploited against users who access legitimate websites with these country-specific domains, making it difficult to distinguish between malicious and legitimate cookie setting. The attack can be executed through various means including cross-site scripting attacks, malicious web pages, or by compromising web servers that serve content to these specific domains. According to ATT&CK framework technique T1548.002, this vulnerability enables privilege escalation through session hijacking, while T1185 represents the related technique of web session hijacking that can be performed using this flaw.
The mitigation strategies for this vulnerability involve multiple layers of defense including immediate browser updates to more recent versions that properly implement cookie domain validation, implementing proper cookie security attributes such as the Secure and HttpOnly flags on all session cookies, and configuring web applications to properly validate cookie domains. Organizations should also implement additional security measures such as using Content Security Policy headers, implementing proper session management with random session identifiers, and ensuring that all web applications enforce strict cookie domain validation. The vulnerability highlights the importance of adhering to RFC 2109 and RFC 2965 standards for cookie handling and demonstrates the critical need for proper security testing of browser components, particularly those related to session management and cookie processing. This case study emphasizes the necessity of comprehensive security reviews of core browser functionalities and the importance of maintaining up-to-date security implementations to prevent exploitation of fundamental session management flaws.