CVE-1999-0710 is a high-severity vulnerability affecting the Squid caching proxy package as distributed in Red Hat Linux versions 5.2 and 6.0, as well as other Linux distributions from that era. The vulnerability arises because the Squid package installs the cachemgr.cgi script in a publicly accessible web directory without adequate access controls. This CGI script is intended for cache management and monitoring but can be exploited by remote attackers as an open proxy or intermediary to connect to other systems. Since the script is accessible over the network without authentication, an attacker can leverage it to relay requests, potentially masking their origin or accessing internal network resources indirectly. The vulnerability has a CVSS v2 score of 7.5, reflecting its network accessibility (AV:N), low attack complexity (AC:L), no authentication required (Au:N), and impacts on confidentiality, integrity, and availability (C:P/I:P/A:P). Although no known exploits are reported in the wild, the presence of this script in a public directory poses a significant risk of misuse. A patch is available from Fedora updates, and applying it or removing/limiting access to cachemgr.cgi is critical to mitigating this threat. Given the age of the affected versions, this vulnerability primarily concerns legacy systems that have not been updated or decommissioned.

For European organizations, the impact of this vulnerability can be substantial if legacy Red Hat Linux 5.2 or 6.0 systems with Squid proxy are still in use, particularly in environments where these proxies are exposed to untrusted networks or the internet. Exploitation could allow attackers to use the vulnerable proxy as a stepping stone to access internal systems, bypass network controls, or anonymize malicious activities. This could lead to unauthorized data disclosure, modification of cached content, or disruption of proxy services, affecting confidentiality, integrity, and availability. Organizations in sectors with strict data protection regulations such as finance, healthcare, and government could face compliance risks and reputational damage if exploited. Additionally, the ability to pivot through the proxy could facilitate further attacks within the network. However, the impact is mitigated by the fact that this vulnerability affects very old Linux versions, which are unlikely to be widely deployed in modern European IT environments.

European organizations should first identify any legacy systems running Red Hat Linux 5.2, 6.0, or other affected distributions with Squid installed. Immediate mitigation steps include applying the official patches available from Fedora update repositories to remove or secure the cachemgr.cgi script. If patching is not feasible, organizations should restrict access to the cachemgr.cgi script by removing it from public web directories or configuring web server access controls to limit usage to trusted administrators only. Network-level controls such as firewall rules should be implemented to block external access to the Squid management interface. Additionally, organizations should consider upgrading legacy systems to supported Linux versions with updated Squid packages. Regular vulnerability scanning and monitoring for unusual proxy usage patterns can help detect exploitation attempts. Finally, documenting and decommissioning outdated systems will reduce exposure to this and similar legacy vulnerabilities.