CVE-1999-0067 in Webserver
Summary
by MITRE
phf cgi program allows remote command execution through shell metacharacters.
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Analysis
by VulDB Data Team • 10/28/2025
The vulnerability identified as CVE-1999-0067 affects the phf cgi program, which is a common component in web servers for handling HTTP requests. This particular flaw resides in the way the program processes input parameters, specifically allowing attackers to inject shell metacharacters that can trigger arbitrary command execution on the affected system. The vulnerability represents a classic example of a command injection flaw that has been documented since the early days of web application security.
The technical implementation of this vulnerability stems from insufficient input validation within the phf cgi program. When the program receives HTTP requests containing specific parameters, it fails to properly sanitize or escape special shell characters such as semicolons, ampersands, or backticks. This allows malicious users to append additional commands to the intended execution path, effectively bypassing normal program boundaries and gaining unauthorized access to the underlying operating system. The flaw operates at the level of shell command construction, where user-supplied data is directly concatenated into shell execution strings without proper sanitization mechanisms.
The operational impact of this vulnerability extends beyond simple unauthorized access, as it provides attackers with complete control over the affected web server. Once exploited, adversaries can execute any commands available on the system, potentially leading to data exfiltration, system compromise, or further lateral movement within the network. The vulnerability is particularly dangerous because it allows for remote exploitation without requiring authentication, making it a prime target for automated attacks and botnet propagation. Organizations running vulnerable versions of the phf cgi program face significant risk of complete system compromise, especially when these systems are publicly accessible.
Security practitioners should implement multiple layers of defense to mitigate this vulnerability, starting with immediate patching of affected systems and removal of vulnerable cgi programs where possible. Network segmentation and firewall rules can help limit exposure by restricting access to web server components that utilize phf or similar vulnerable programs. Additionally, input validation should be implemented at multiple levels including web application firewalls, server-side validation, and proper output encoding. This vulnerability aligns with CWE-78 which describes improper neutralization of special elements used in os command injection attacks, and maps to ATT&CK technique T1059.007 for command and scripting interpreter. Organizations should also conduct regular vulnerability assessments and maintain up-to-date security monitoring to detect potential exploitation attempts. The remediation process involves not only patching the specific vulnerability but also implementing broader security practices such as least privilege access, regular security updates, and comprehensive application security testing to prevent similar issues from arising in other components.