CVE-1999-1004 is a medium-severity buffer overflow vulnerability found in the POP server component called POProxy, which is part of the Norton Anti-Virus protection program NAV2000. The vulnerability arises when the POP server processes an excessively large USER command, causing a buffer overflow condition. This overflow can potentially disrupt the availability of the POP service by crashing the server or causing it to behave unpredictably. The vulnerability does not affect confidentiality or integrity directly, as it does not allow unauthorized data access or modification, but it impacts availability by enabling denial-of-service (DoS) conditions. The vulnerability is remotely exploitable over the network without requiring authentication, making it accessible to any attacker who can reach the POP server. The CVSS score of 5.0 reflects this moderate risk, with the vector indicating network attack vector (AV:N), low attack complexity (AC:L), no authentication required (Au:N), no impact on confidentiality or integrity (C:N/I:N), and partial impact on availability (A:P). There is no patch available for this vulnerability, and no known exploits have been reported in the wild. Given the age of the vulnerability (published in 1999) and the specific affected product version (Norton Anti-Virus 2000), modern systems are unlikely to be affected unless legacy systems are still in use. The vulnerability is primarily a denial-of-service threat against the POP server component of NAV2000.

For European organizations, the primary impact of this vulnerability is the potential disruption of email services relying on the vulnerable POP server component of Norton Anti-Virus NAV2000. This could lead to temporary denial of service for users accessing their email via POP, affecting business communications and productivity. Since the vulnerability does not allow data theft or modification, the risk to sensitive information is low. However, organizations running legacy systems with this outdated antivirus solution could face operational interruptions. Additionally, if the POP server is exposed to the internet, attackers could exploit this vulnerability to cause service outages. The lack of a patch means organizations must rely on mitigation strategies or upgrade paths. Given the age and specificity of the vulnerability, the impact is limited to environments still using this obsolete software.

Since no patch is available for this vulnerability, European organizations should consider the following specific mitigation steps: 1) Immediately discontinue use of Norton Anti-Virus NAV2000 and upgrade to a current, supported antivirus solution that does not include the vulnerable POP server component. 2) If upgrading is not immediately possible, restrict network access to the POP server component by implementing firewall rules that block incoming connections to the POP service port (usually TCP port 110) from untrusted networks, especially the internet. 3) Monitor network traffic for unusual or large USER command attempts targeting the POP server to detect potential exploitation attempts. 4) Consider disabling the POProxy POP server component if it is not required for business operations. 5) Implement network segmentation to isolate legacy systems running NAV2000 from critical infrastructure and sensitive data environments. 6) Educate IT staff about the risks of running outdated antivirus software and the importance of timely upgrades and patching.