CVE-2016-7125 in PHP
Summary
by MITRE
ext/session/session.c in PHP before 5.6.25 and 7.x before 7.0.10 skips invalid session names in a way that triggers incorrect parsing, which allows remote attackers to inject arbitrary-type session data by leveraging control of a session name, as demonstrated by object injection.
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Analysis
by VulDB Data Team • 09/15/2022
The vulnerability identified as CVE-2016-7125 represents a critical session management flaw in PHP versions prior to 5.6.25 and 7.0.10. This issue resides within the ext/session/session.c file and demonstrates how improper handling of invalid session names can lead to severe security implications. The flaw occurs when PHP processes session data and encounters malformed session identifiers, creating a parsing anomaly that attackers can exploit to manipulate session contents.
The technical implementation of this vulnerability stems from how PHP's session handling mechanism processes session names that contain invalid characters or control sequences. When PHP encounters such invalid session names, it skips them in a manner that disrupts the normal session parsing flow, allowing attackers to inject malicious session data that bypasses standard validation checks. This behavior creates a condition where session data can be manipulated to include arbitrary data types, including serialized objects that can be executed when the session data is later processed.
From an operational perspective, this vulnerability enables remote attackers to perform object injection attacks through session manipulation. The impact extends beyond simple data corruption as attackers can leverage this weakness to execute arbitrary code within the PHP application context, potentially leading to full system compromise. The vulnerability is particularly dangerous because it operates at the session layer, affecting applications that rely heavily on session-based authentication and data storage mechanisms.
The exploitation of CVE-2016-7125 aligns with several ATT&CK techniques including T1190 for exploitation of remote services and T1059 for command and scripting interpreter usage. This vulnerability maps to CWE-502 which specifically addresses deserialization of untrusted data, making it a prime example of how session management flaws can create pathways for code execution. Organizations using affected PHP versions face significant risk as this vulnerability can be exploited without authentication, making it particularly attractive to threat actors targeting web applications.
Security mitigations for this vulnerability primarily involve immediate patching of PHP installations to versions 5.6.25 or 7.0.10 and later. Additionally, implementing proper session name validation at the application level can provide additional defense in depth. Organizations should also consider implementing session management best practices such as using secure session identifiers, implementing proper session expiration mechanisms, and monitoring for unusual session data patterns. The vulnerability underscores the importance of proper input validation and error handling in session management components, highlighting how seemingly minor parsing issues can create significant security risks that align with the principle of least privilege and secure coding practices recommended by industry standards.