CVE-2007-3799 in PHP
Summary
by MITRE
The session_start function in ext/session in PHP 4.x up to 4.4.7 and 5.x up to 5.2.3 allows remote attackers to insert arbitrary attributes into the session cookie via special characters in a cookie that is obtained from (1) PATH_INFO, (2) the session_id function, and (3) the session_start function, which are not encoded or filtered when the new session cookie is generated, a related issue to CVE-2006-0207.
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Analysis
by VulDB Data Team • 04/26/2025
The vulnerability described in CVE-2007-3799 represents a critical session management flaw in PHP versions 4.x through 4.4.7 and 5.x through 5.2.3. This issue specifically targets the session_start function within PHP's ext/session extension, where improper handling of special characters in session identifiers creates opportunities for attackers to manipulate session cookies. The vulnerability stems from insufficient input validation and encoding mechanisms when processing session data obtained through three primary vectors including PATH_INFO parsing, the session_id function, and the session_start function itself. Attackers can exploit this weakness by crafting malicious cookies containing special characters that bypass normal filtering mechanisms, allowing them to inject arbitrary attributes into session cookies.
The technical implementation of this vulnerability involves the improper sanitization of session identifiers during the cookie generation process. When PHP processes session data from PATH_INFO, it does not adequately encode or filter special characters that may be present in the session identifier. This weakness enables attackers to inject malicious content into the session cookie structure, potentially allowing for session hijacking or manipulation of session attributes. The flaw is particularly dangerous because it operates at the core session management layer of PHP applications, affecting the fundamental security mechanisms that protect user sessions. This issue is categorized under CWE-20 as "Improper Input Validation" and represents a related problem to CVE-2006-0207, indicating a pattern of session-related vulnerabilities in PHP's handling of user-supplied data.
The operational impact of CVE-2007-3799 extends beyond simple session manipulation to potentially enable complete session compromise. Attackers can exploit this vulnerability to inject malicious attributes into session cookies, which may allow them to escalate privileges, access unauthorized resources, or maintain persistent access to user sessions. The vulnerability affects web applications that rely on PHP's built-in session management, making it particularly widespread across the internet. In practical attack scenarios, an attacker could craft a malicious URL containing special characters in the PATH_INFO component, which when processed by PHP's session_start function, would result in a malformed session cookie containing injected attributes. This weakness directly impacts the integrity and confidentiality of session data, potentially allowing for unauthorized access to sensitive application resources.
Mitigation strategies for this vulnerability require immediate patching of affected PHP versions to the latest stable releases that address the session cookie encoding issues. Organizations should implement proper input validation and sanitization for all session-related data processing, ensuring that special characters are properly encoded before being included in session cookies. The implementation of secure session management practices including the use of secure flags, HttpOnly attributes, and proper session regeneration mechanisms provides additional defense layers. Security teams should also monitor application logs for unusual session cookie patterns and implement web application firewalls to detect and block malicious session manipulation attempts. From an ATT&CK framework perspective, this vulnerability maps to T1548.003 (Abuse Elevation Control Mechanism) and T1185 (Man in the Middle) techniques, as it enables attackers to manipulate session attributes and potentially intercept or modify session data during transmission. Regular security assessments and vulnerability scanning should include checks for this specific session handling weakness to prevent exploitation in production environments.