CVE-2012-0475 in Firefox
Summary
by MITRE
Mozilla Firefox 4.x through 11.0, Thunderbird 5.0 through 11.0, and SeaMonkey before 2.9 do not properly construct the Origin and Sec-WebSocket-Origin HTTP headers, which might allow remote attackers to bypass an IPv6 literal ACL via a cross-site (1) XMLHttpRequest or (2) WebSocket operation involving a nonstandard port number and an IPv6 address that contains certain zero fields.
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Analysis
by VulDB Data Team • 03/24/2021
This vulnerability affects Mozilla Firefox versions 4.x through 11.0, Thunderbird versions 5.0 through 11.0, and SeaMonkey versions before 2.9, representing a significant security flaw in web browser and email client implementations. The issue stems from improper construction of HTTP headers, specifically the Origin and Sec-WebSocket-Origin headers, which are critical components in web security mechanisms designed to prevent cross-site scripting attacks and enforce security policies. These headers are essential for implementing the same-origin policy that protects web applications from malicious cross-origin requests.
The technical flaw manifests when browsers handle IPv6 addresses containing zero fields in conjunction with nonstandard port numbers during cross-site XMLHttpRequest or WebSocket operations. When an IPv6 address contains zero fields, the browser's header construction process fails to properly normalize or validate these addresses, creating a potential bypass mechanism for access control lists. This vulnerability is particularly concerning because IPv6 addresses with zero compression can be represented in multiple valid formats, and the inconsistent handling of these formats in header construction creates security gaps that attackers can exploit.
The operational impact of this vulnerability allows remote attackers to bypass IPv6 literal access control lists by crafting malicious requests that exploit the inconsistent header construction. Attackers can potentially perform cross-site operations that would normally be blocked by security policies, enabling unauthorized access to resources that should be protected. This affects both XMLHttpRequest operations, which are fundamental to web application communication, and WebSocket operations that provide full-duplex communication channels. The vulnerability specifically targets scenarios involving nonstandard ports, making it particularly dangerous in environments where applications use non-standard network configurations.
This weakness aligns with CWE-284, which addresses improper access control in software implementations, and relates to the broader category of web security vulnerabilities involving header manipulation and cross-origin resource sharing. From an ATT&CK framework perspective, this vulnerability maps to techniques involving privilege escalation and evasion of security controls, specifically targeting the defense mechanisms that rely on proper header validation and origin checking. The vulnerability demonstrates how seemingly minor implementation details in HTTP header construction can create significant security weaknesses that affect the fundamental security model of web browsers and email clients.
The mitigation strategy involves updating to patched versions of the affected software products, which typically include proper normalization of IPv6 addresses in header construction and enhanced validation of address formats. Organizations should implement network monitoring to detect suspicious header patterns and consider deploying additional security controls such as web application firewalls that can detect and block malformed headers. Regular security assessments of browser configurations and network policies are essential to prevent exploitation of this type of vulnerability, particularly in environments where IPv6 addressing is prevalent and nonstandard ports are commonly used for web applications.