CVE-1999-0951 is a critical buffer overflow vulnerability found in the OmniHTTPd web server, specifically within the CGI program imagemap.exe. OmniHTTPd is a lightweight web server developed by Omnicron, with affected versions including 1.1 and 2.4pro. The vulnerability arises due to improper bounds checking in the imagemap.exe CGI application, which processes user-supplied input. An attacker can exploit this flaw by sending specially crafted HTTP requests that overflow the buffer allocated for input data. This overflow can overwrite adjacent memory, allowing the attacker to execute arbitrary commands on the affected server remotely without any authentication or user interaction. The vulnerability has a CVSS v2 base score of 10.0, indicating maximum severity, with an attack vector of network (remote), low attack complexity, no authentication required, and full impact on confidentiality, integrity, and availability. Despite its age (published in 1999), this vulnerability remains critical because it allows complete system compromise remotely. No patches or fixes are available, and no known exploits have been reported in the wild, but the theoretical risk remains high for any legacy systems still running these OmniHTTPd versions with imagemap.exe enabled.

For European organizations, the impact of this vulnerability can be severe if legacy systems running OmniHTTPd 1.1 or 2.4pro with imagemap.exe are still in use, particularly in industrial, governmental, or research environments where older software may persist. Successful exploitation would allow attackers to execute arbitrary commands remotely, potentially leading to full system compromise, data theft, disruption of services, or use of the compromised server as a pivot point for further attacks within the network. Confidentiality, integrity, and availability of affected systems would be fully compromised. Given the lack of patches, organizations relying on these versions face a significant risk if exposed to the internet or accessible networks. Although OmniHTTPd is not widely used today, any remaining deployments in critical infrastructure or legacy systems could be targeted by attackers seeking easy remote code execution vectors.

Since no official patches are available, European organizations should prioritize the following mitigations: 1) Identify and inventory all systems running OmniHTTPd versions 1.1 or 2.4pro, especially those exposing imagemap.exe. 2) Immediately disable or remove the imagemap.exe CGI program to eliminate the vulnerable component. 3) If possible, upgrade or migrate to modern, supported web server software that does not contain this vulnerability. 4) Implement network-level protections such as firewall rules to restrict access to affected servers and limit exposure to trusted internal networks only. 5) Employ intrusion detection/prevention systems (IDS/IPS) with signatures for buffer overflow attempts targeting imagemap.exe. 6) Monitor logs for unusual or suspicious HTTP requests that could indicate exploitation attempts. 7) For legacy systems that cannot be upgraded, consider isolating them in segmented network zones with strict access controls to minimize risk.