CVE-2006-0887 in PHPLib
Summary
by MITRE
Eval injection vulnerability in sessions.inc in PHP Base Library (PHPLib) before 7.4a, when index.php3 from the PHPLib distribution is available on the server, allows remote attackers to execute arbitrary PHP code by including a base64-encoded representation of the code in a cookie. NOTE: this description was significantly updated on 20060605 to reflect new details after an initial vague advisory.
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Analysis
by VulDB Data Team • 07/19/2018
The CVE-2006-0887 vulnerability represents a critical server-side code injection flaw within the PHP Base Library (PHPLib) ecosystem, specifically targeting the sessions.inc component. This vulnerability emerged in PHPLib versions prior to 7.4a and exploited a fundamental design flaw in how the library handled user-supplied data within cookie parameters. The attack vector became possible when the index.php3 file from the PHPLib distribution remained accessible on the web server, creating an exploitable entry point that could be leveraged by remote adversaries. The vulnerability operates through a sophisticated manipulation of the cookie parameter mechanism, where attackers could inject malicious PHP code by encoding it in base64 format within the cookie values, effectively bypassing normal input validation measures.
The technical exploitation of this vulnerability stems from improper input sanitization and unsafe code execution practices within the PHPLib session handling mechanism. When the vulnerable sessions.inc file processed cookie data, it failed to properly validate or escape the input before incorporating it into PHP execution contexts. This flaw aligns with CWE-94, which classifies the vulnerability as an "Improper Control of Generation of Code ('Code Injection')" where attacker-controllable data is executed as code. The base64 encoding component of the attack serves as a sophisticated obfuscation technique that helps evade basic detection mechanisms while maintaining the integrity of the malicious payload. Attackers could craft specially formatted cookies containing base64-encoded PHP commands that would be decoded and executed by the vulnerable server-side code, potentially leading to complete system compromise.
The operational impact of CVE-2006-0887 extends far beyond simple code execution, representing a severe threat to web application security and server integrity. Successful exploitation could enable attackers to execute arbitrary PHP commands with the privileges of the web server process, potentially allowing for complete system takeover, data exfiltration, and persistence mechanisms. The vulnerability's remote nature means that attackers could exploit it from anywhere on the internet without requiring local access or authentication. From an attacker's perspective, this vulnerability maps directly to ATT&CK technique T1059.007, which covers "Command and Scripting Interpreter: Python" and similar execution techniques, though in this case it involves PHP command execution. The attack could lead to unauthorized access to sensitive data, modification of web content, creation of backdoors, and establishment of persistent access points within the compromised environment.
Mitigation strategies for this vulnerability require immediate patching of affected PHPLib installations to version 7.4a or later, where the code injection flaws have been addressed through proper input validation and sanitization. Organizations should implement comprehensive cookie validation mechanisms that reject or sanitize any suspicious content before processing, particularly focusing on preventing base64-encoded payloads from being executed. Network-level protections such as web application firewalls can help detect and block suspicious cookie patterns, though these should complement rather than replace proper code fixes. Security monitoring should include detection of unusual cookie patterns and base64 decoding activities that might indicate exploitation attempts. Additionally, administrators should conduct thorough audits of web applications to identify any other potential uses of vulnerable PHPLib components and ensure that all affected systems are properly updated and patched according to vendor security advisories. The vulnerability serves as a critical reminder of the importance of secure coding practices and proper input validation in preventing code injection attacks that can lead to complete system compromise.