CVE-1999-0058 in PHP
Summary
by MITRE
Buffer overflow in PHP cgi program, php.cgi allows shell access.
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Analysis
by VulDB Data Team • 04/16/2026
The vulnerability identified as CVE-1999-0058 represents a critical buffer overflow flaw within the PHP CGI implementation that was prevalent in early web server configurations. This issue specifically affected the php.cgi program which served as the gateway interface between web servers and PHP scripting environments. The vulnerability emerged from inadequate input validation mechanisms within the CGI handler, allowing malicious actors to exploit memory handling flaws in the program's execution flow. The buffer overflow occurred when the cgi program processed user-supplied input parameters without proper bounds checking, creating opportunities for attackers to overwrite adjacent memory locations with malicious code.
The technical exploitation of this vulnerability leveraged the fundamental weakness in how the php.cgi program managed memory allocation for input buffers. When web servers passed request parameters to the PHP CGI handler, the program failed to validate the length of incoming data before copying it into fixed-size buffers. This flaw directly maps to CWE-121, which describes stack-based buffer overflow conditions, and CWE-122, which covers heap-based buffer overflow scenarios. Attackers could craft specially formatted HTTP requests containing excessive input data that would exceed the allocated buffer boundaries, causing the program to overwrite critical memory regions including return addresses and function pointers. The overflow could be carefully orchestrated to redirect program execution flow to malicious code injected into the buffer space, effectively providing attackers with shell access to the underlying system.
The operational impact of CVE-1999-0058 was severe and far-reaching across web server environments that relied on PHP CGI implementations. Organizations running vulnerable configurations faced immediate risks of complete system compromise, as successful exploitation granted attackers full command-line access to the affected servers. The vulnerability was particularly dangerous because it allowed remote code execution without requiring authentication, making it an attractive target for automated attacks. Security professionals noted that the exploit could be reliably reproduced across different operating systems and web server platforms where PHP CGI was deployed, including apache and other common web servers of the era. The vulnerability also enabled attackers to escalate privileges and potentially gain access to sensitive data stored on the compromised systems, making it a significant threat to web application security and data integrity.
Mitigation strategies for CVE-1999-0058 required immediate action from system administrators and security teams to protect their web server infrastructure. The most effective approach involved upgrading to patched versions of PHP that addressed the buffer overflow conditions in the CGI implementation, typically through version updates that included proper input validation and memory management controls. Organizations were advised to disable the CGI version of PHP and migrate to more secure FastCGI implementations or PHP modules integrated directly with web servers, which provided better memory protection mechanisms. Network-level protections such as web application firewalls and input filtering rules could help detect and block malicious requests attempting to exploit the vulnerability. Additionally, security practices recommended implementing proper access controls and privilege separation to limit the potential damage from successful exploits, while regular security assessments and code reviews helped identify similar vulnerabilities in other applications and system components. The incident highlighted the importance of secure coding practices and proper input validation, aligning with ATT&CK technique T1059 for command and script injection, emphasizing the need for comprehensive defensive measures against remote code execution vulnerabilities.