CVE-2011-4718 in PHP
Summary
by MITRE
Session fixation vulnerability in the Sessions subsystem in PHP before 5.5.2 allows remote attackers to hijack web sessions by specifying a session ID.
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Analysis
by VulDB Data Team • 05/21/2021
The CVE-2011-4718 vulnerability represents a critical session fixation flaw within PHP's session management subsystem that existed prior to version 5.5.2. This vulnerability falls under the CWE-384 category of Session Fixation, which is classified as a serious weakness in web application security. The flaw enables remote attackers to exploit the session handling mechanism by manipulating session identifiers, effectively allowing unauthorized users to hijack active user sessions and gain unauthorized access to protected resources. The vulnerability specifically affects the way PHP processes session IDs during the authentication process, creating a window of opportunity for malicious actors to establish a known session ID that can be used to impersonate legitimate users.
The technical implementation of this vulnerability stems from PHP's session handling logic where session IDs are not properly regenerated upon successful authentication. When a user logs in, the system should invalidate the previous session ID and generate a new one to prevent session fixation attacks. However, in vulnerable versions of PHP, the system would accept and continue using the same session ID even after authentication, allowing an attacker who knows the session ID to reuse it and gain access to the user's authenticated session. This flaw typically occurs when applications do not explicitly call session_regenerate_id() function after authentication, leaving the session ID unchanged and vulnerable to exploitation.
The operational impact of CVE-2011-4718 is severe and far-reaching across web applications built on PHP platforms. Attackers can leverage this vulnerability to perform session hijacking attacks, where they capture a valid session ID from a user and then use it to impersonate that user. This allows unauthorized access to sensitive data, privileged operations, and confidential information within the web application. The attack vector is particularly dangerous because it requires minimal technical expertise to execute and can be automated through various exploitation tools. Organizations using vulnerable PHP versions face significant risk of data breaches, unauthorized transactions, and potential system compromise. The vulnerability also impacts compliance with security standards such as those outlined in the OWASP Top Ten, specifically addressing the session management weakness that can lead to unauthorized access.
Mitigation strategies for CVE-2011-4718 involve both immediate patching and code-level remediation approaches. The primary solution is to upgrade to PHP version 5.5.2 or later, where the session handling has been improved to prevent session fixation attacks. Additionally, developers should implement proper session management practices including calling session_regenerate_id(true) after successful authentication to ensure that session IDs are regenerated with each login event. This practice aligns with the ATT&CK technique T1563.002 for credential access and helps prevent session hijacking by ensuring that old session identifiers become invalid upon user authentication. Organizations should also implement additional security measures such as secure session cookie attributes, proper session timeout configurations, and regular security audits of their PHP applications to identify and remediate similar vulnerabilities in their codebase.