CVE-1999-1246 is a high-severity vulnerability affecting Microsoft Site Server 3.0, specifically its Direct Mailer feature. The vulnerability arises because the Direct Mailer component saves user domain names and passwords in plaintext within the TMLBQueue network share. This share is configured with insecure default permissions, which means that remote attackers can access it without authentication. By reading these plaintext credentials, attackers can escalate privileges within the affected environment. The vulnerability has a CVSS 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). Since the passwords are stored in plaintext and accessible remotely, attackers can easily harvest credentials to compromise user accounts and potentially gain administrative control over the Site Server or connected systems. No patches or fixes are available, and no known exploits have been reported in the wild, but the risk remains significant due to the nature of the exposure and the criticality of the credentials involved.

For European organizations using Microsoft Site Server 3.0, this vulnerability poses a serious risk of credential theft leading to unauthorized access and privilege escalation. Compromise of domain credentials can result in widespread access to internal networks, sensitive data exposure, and disruption of services. Given that Site Server 3.0 is an older product, organizations still running it may be operating legacy systems critical to business operations, increasing the potential impact. Attackers exploiting this vulnerability could manipulate or disrupt mail services, access confidential user data, or pivot to other internal systems. The vulnerability affects confidentiality (exposure of passwords), integrity (potential unauthorized changes), and availability (possible service disruption). The ease of exploitation without authentication and over the network makes it a significant threat, especially in environments where network segmentation and access controls are weak or outdated.

Since no official patch is available, European organizations should prioritize the following mitigations: 1) Immediately restrict access permissions on the TMLBQueue network share to the minimum necessary, ideally limiting it to trusted administrators only. 2) Remove or disable the Direct Mailer feature if it is not actively used, to eliminate the storage of plaintext credentials. 3) Conduct a thorough audit of all systems running Microsoft Site Server 3.0 and plan for migration to supported, updated platforms to reduce exposure to legacy vulnerabilities. 4) Implement network segmentation to isolate legacy servers from general user networks and the internet. 5) Monitor network shares and logs for unauthorized access attempts to the TMLBQueue share. 6) Enforce strong password policies and consider resetting domain credentials that may have been exposed. 7) Employ intrusion detection systems to detect anomalous access patterns related to this vulnerability. These steps go beyond generic advice by focusing on immediate containment of the exposed credentials and long-term elimination of the vulnerable software.