CVE-1999-1555 is a high-severity vulnerability affecting Cheyenne InocuLAN Anti-Virus Server version 4.0 prior to Service Pack 2. The vulnerability arises because the software creates an update directory with overly permissive access controls, specifically granting "EVERYONE FULL CONTROL" permissions. This misconfiguration allows any local user on the affected system to manipulate the antivirus update mechanism by placing a malicious Trojan horse DLL into the update directory. When the antivirus server processes updates, it may load this malicious DLL, leading to arbitrary code execution with the privileges of the antivirus service. The vulnerability does not require authentication, but local access is necessary. The CVSS v2 score is 7.2, reflecting the high impact on confidentiality, integrity, and availability, combined with low attack complexity and no authentication requirement. Since the product is an antivirus server, exploitation could undermine the security infrastructure itself, potentially allowing attackers to disable or subvert malware detection and remediation capabilities. No patch is available, and no known exploits in the wild have been reported, but the risk remains significant due to the nature of the flaw and the critical role of the affected software.

For European organizations, this vulnerability poses a serious risk to endpoint and network security. Compromise of the antivirus server could lead to widespread infection by malware, as attackers could disable or manipulate antivirus updates and scanning processes. This could result in data breaches, loss of data integrity, and disruption of business operations. Organizations relying on Cheyenne InocuLAN Anti-Virus Server 4.0 or similar legacy systems may face increased exposure, especially if local user accounts are not tightly controlled. The vulnerability could be exploited by malicious insiders or attackers who gain local access through other means. Given the critical role of antivirus infrastructure in protecting sensitive data and systems, exploitation could have cascading effects on compliance with European data protection regulations such as GDPR, potentially leading to legal and financial consequences.

Since no official patch is available, European organizations should consider the following specific mitigation steps: 1) Immediately restrict local user permissions on systems running Cheyenne InocuLAN Anti-Virus Server to trusted administrators only, removing unnecessary local user accounts. 2) Manually modify the permissions of the update directory to remove "EVERYONE FULL CONTROL" and restrict access to only the antivirus service account and administrators. 3) Monitor the update directory for unauthorized file changes or additions, employing file integrity monitoring tools. 4) If possible, upgrade or migrate from the outdated Cheyenne InocuLAN Anti-Virus Server to a modern, supported antivirus solution with active vendor support and patching. 5) Implement strict local access controls and endpoint security policies to prevent unauthorized local access. 6) Conduct regular audits of antivirus server configurations and permissions to ensure no regressions occur. 7) Educate IT staff about the risks of legacy software and the importance of timely upgrades and patching.