CVE-2000-0319 is a vulnerability found in the mail.local component of Sendmail versions 5.58 through 8.9.3, including multiple 8.x releases. The issue arises because mail.local does not correctly identify the end-of-message delimiter string ".\n". This delimiter is critical in SMTP and local mail delivery to mark the end of the message body. The vulnerability allows a remote attacker to craft a specially formatted email message containing a line exactly 2047 characters long that ends with ".\n". Due to improper parsing, this can cause mail.local to either crash or corrupt mailboxes, resulting in a denial of service (DoS) condition. The vulnerability does not affect confidentiality or integrity of the mail content directly, but availability is impacted as mail delivery services can be disrupted or mailboxes corrupted, potentially leading to loss of mail data. The attack requires no authentication and can be triggered remotely by sending a malicious email to a vulnerable system. The CVSS v2 score is 5.0 (medium severity), reflecting the ease of exploitation (network accessible, no auth) but limited impact scope (availability only). No patches are available as this is an old vulnerability dating back to 2000, and no known exploits have been reported in the wild recently. However, legacy systems still running these Sendmail versions remain at risk if exposed to untrusted email sources.

For European organizations, the primary impact is disruption of email services due to denial of service or mailbox corruption. This can affect business continuity, especially for organizations relying on legacy mail infrastructure with Sendmail 8.10.x or earlier versions. Loss of mailbox integrity can lead to loss of important communications and operational delays. While the vulnerability does not allow data theft or privilege escalation, the availability impact can be significant for critical communication systems. Organizations in sectors such as government, finance, healthcare, and critical infrastructure that may still use legacy Sendmail installations could face operational risks. Additionally, organizations with less mature IT environments or those in transition phases might be more vulnerable to this issue. The lack of patches means mitigation relies on configuration and network controls. Given the age of the vulnerability, modern mail systems are unlikely to be affected, but legacy systems in Europe remain a concern.

1. Upgrade or replace legacy Sendmail installations with modern, supported mail transfer agents (MTAs) that have patched this vulnerability or are not susceptible to it. 2. If upgrading is not immediately possible, implement strict email filtering and validation at the network perimeter to block or quarantine emails containing suspiciously long lines, especially those approaching or exceeding 2047 characters ending with ".\n". 3. Employ network segmentation to isolate legacy mail servers from untrusted networks and reduce exposure to malicious emails. 4. Monitor mail server logs for abnormal message patterns or crashes that could indicate exploitation attempts. 5. Consider deploying intrusion detection/prevention systems (IDS/IPS) with signatures tuned to detect this specific attack vector. 6. Regularly back up mailboxes and mail server configurations to enable recovery in case of mailbox corruption. 7. Educate IT staff about the risks of legacy mail systems and encourage migration planning to supported platforms. These steps go beyond generic advice by focusing on legacy system isolation, proactive filtering of specific message characteristics, and operational readiness for recovery.