CVE-2011-2605 in Firefox
Summary
by MITRE
CRLF injection vulnerability in the nsCookieService::SetCookieStringInternal function in netwerk/cookie/nsCookieService.cpp in Mozilla Firefox before 3.6.18 and 4.x through 4.0.1, and Thunderbird before 3.1.11, allows remote attackers to bypass intended access restrictions via a string containing a \n (newline) character, which is not properly handled in a JavaScript "document.cookie =" expression, a different vulnerability than CVE-2011-2374.
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Analysis
by VulDB Data Team • 11/13/2021
The CVE-2011-2605 vulnerability represents a critical cross-site scripting and access control bypass flaw found in Mozilla Firefox and Thunderbird email clients. This vulnerability stems from improper handling of carriage return and line feed characters within the cookie management system, specifically within the nsCookieService::SetCookieStringInternal function. The flaw exists in versions prior to Firefox 3.6.18 and 4.x through 4.0.1, as well as Thunderbird versions before 3.1.11, making it a widespread issue affecting multiple browser and email client versions from 2011.
The technical exploitation of this vulnerability occurs when a malicious web server or attacker crafts a cookie string containing newline characters that are not properly sanitized or escaped during processing. When the JavaScript document.cookie = "..." expression processes these malformed cookie strings, the newline characters can be interpreted as separate cookie assignments, allowing attackers to inject additional cookie data that bypasses normal access controls. This CRLF (Carriage Return Line Feed) injection technique enables attackers to manipulate cookie values in ways that were never intended by the application's security model. The vulnerability specifically affects how cookie strings are parsed and validated before being stored or transmitted, creating a path for unauthorized cookie manipulation.
The operational impact of CVE-2011-2605 is significant as it allows remote attackers to bypass authentication mechanisms, session management controls, and access restrictions that depend on proper cookie handling. Attackers can potentially steal session cookies, manipulate user permissions, or gain unauthorized access to protected resources by injecting malicious cookie data through the CRLF injection vector. This vulnerability particularly affects web applications that rely heavily on cookie-based authentication and session management, as it undermines the fundamental security assumptions about how cookie data is processed and validated. The attack vector is particularly dangerous because it can be executed through standard web browsing activities without requiring any special privileges or user interaction beyond visiting a malicious website.
This vulnerability aligns with CWE-113, which specifically addresses "Improper Neutralization of CRLF Sequences in HTTP Headers" and is related to the broader category of injection flaws that have been extensively documented in the OWASP Top 10. The attack pattern follows techniques described in the MITRE ATT&CK framework under the 'Command and Scripting Interpreter' and 'Data Manipulation' tactics, where adversaries manipulate data structures to achieve unauthorized access. Organizations should implement proper input validation and sanitization of cookie data, particularly when processing user-supplied values. The recommended mitigations include updating to patched versions of affected software, implementing strict cookie validation mechanisms, and ensuring that all cookie data is properly escaped before being processed by JavaScript cookie manipulation functions. Additionally, network administrators should monitor for suspicious cookie patterns and implement web application firewalls that can detect and block CRLF injection attempts in HTTP headers and cookie values.