CVE-2008-2050 in PHP
Summary
by MITRE
Stack-based buffer overflow in the FastCGI SAPI (fastcgi.c) in PHP before 5.2.6 has unknown impact and attack vectors.
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Analysis
by VulDB Data Team • 08/10/2019
The vulnerability identified as CVE-2008-2050 represents a critical stack-based buffer overflow flaw within PHP's FastCGI Server Application Programming Interface implementation. This security defect resides in the fastcgi.c source file and affects PHP versions prior to 5.2.6, making it a significant concern for web application security. The vulnerability stems from inadequate input validation and memory management practices within the FastCGI protocol handling code, which processes requests from web servers to PHP applications. The buffer overflow occurs when the application fails to properly check the length of incoming data before copying it into fixed-size stack buffers, creating opportunities for malicious input to overwrite adjacent memory locations.
The technical nature of this vulnerability places it squarely within CWE-121, which categorizes stack-based buffer overflows as a fundamental memory safety issue. Such flaws typically arise when developers assume that input data will not exceed predetermined limits without implementing proper boundary checks. The FastCGI SAPI implementation in PHP processes external requests through the FastCGI protocol, which allows web servers to communicate with PHP applications in a more efficient manner than traditional CGI. When malformed input reaches the fastcgi.c module, the insufficient buffer size validation causes the program to write beyond allocated memory boundaries, potentially leading to arbitrary code execution or application crashes.
The operational impact of this vulnerability extends beyond simple denial-of-service conditions, as stack-based buffer overflows often provide attackers with opportunities for privilege escalation and remote code execution. Attackers can craft malicious FastCGI requests that exploit the buffer overflow to overwrite critical memory segments including return addresses, function pointers, or other control data structures. This vulnerability affects web applications deployed on servers using PHP with FastCGI support, particularly those running vulnerable versions of PHP before 5.2.6. The attack vectors remain unspecified in the original CVE description, but typically involve sending specially crafted requests through FastCGI-enabled web servers such as nginx or Apache with mod_fastcgi. The vulnerability's exploitation potential aligns with ATT&CK technique T1203, which covers exploitation of software vulnerabilities for privilege escalation, and T1059, which encompasses command and scripting interpreters.
Mitigation strategies for CVE-2008-2050 primarily focus on immediate version upgrades to PHP 5.2.6 or later, which contain the necessary patches to address the buffer overflow. Organizations should also implement network-level protections such as firewalls and intrusion detection systems to monitor and restrict FastCGI traffic, particularly when FastCGI is exposed to untrusted networks. Additionally, input validation should be strengthened at multiple layers including web server configurations, application-level filters, and database interactions to reduce the attack surface. Security monitoring should include regular vulnerability assessments of PHP installations and their FastCGI configurations, along with maintaining up-to-date security patches for all web server components. The vulnerability serves as a reminder of the critical importance of proper memory management in server-side applications and the necessity of comprehensive security testing, particularly for components handling external input through protocols like FastCGI that are integral to modern web infrastructure.