CVE-1999-0107 is a buffer overflow vulnerability affecting Apache HTTP Server versions 1.2.5 and earlier, including versions as early as 0.8.11 through 1.2.5. The vulnerability arises when the server processes a large number of HTTP GET requests containing an excessive number of '/' characters. This malformed input causes a buffer overflow condition within the server's request handling code, which can be exploited remotely without authentication. The primary impact of this vulnerability is a denial of service (DoS), where the server becomes unresponsive or crashes due to memory corruption triggered by the overflow. The vulnerability does not affect confidentiality or integrity directly, as it does not allow code execution or data leakage, but it disrupts availability. The CVSS v2 score of 5.0 (medium severity) reflects the network vector (remote exploitation), low attack complexity, no authentication required, and impact limited to availability. No patches are available for this vulnerability, likely due to its age and the obsolescence of the affected Apache versions. No known exploits have been reported in the wild, which may be due to the rarity of these legacy versions in current use. However, systems still running these outdated Apache versions remain vulnerable to remote DoS attacks via crafted HTTP GET requests.

For European organizations, the impact of this vulnerability depends largely on whether legacy Apache HTTP Server versions 1.2.5 or earlier are still in operation. In modern environments, these versions are generally obsolete and replaced by more recent, secure releases. However, some legacy industrial control systems, embedded devices, or archival servers might still run these old versions, especially in sectors with long equipment lifecycles such as manufacturing, utilities, or government infrastructure. An attacker exploiting this vulnerability could remotely cause service outages, disrupting web services and potentially affecting business continuity. This could lead to operational downtime, loss of customer trust, and potential regulatory scrutiny if critical services are impacted. Given the vulnerability only causes denial of service without data compromise, the confidentiality and integrity risks are minimal. Nonetheless, availability disruption can have significant operational and reputational consequences, particularly for organizations relying on continuous web service availability.

Since no official patches are available for this vulnerability, European organizations should prioritize upgrading to supported, secure versions of Apache HTTP Server well beyond 1.2.5. Migration to current Apache releases (2.x or later) will inherently resolve this vulnerability and provide improved security and performance. For legacy systems that cannot be upgraded immediately, organizations should implement network-level protections such as web application firewalls (WAFs) or intrusion prevention systems (IPS) configured to detect and block HTTP GET requests with abnormally long or excessive '/' characters. Rate limiting and request filtering can also reduce the risk of DoS attacks exploiting this flaw. Additionally, isolating legacy servers from direct internet exposure and restricting access to trusted networks can minimize attack surface. Regular monitoring of server logs for unusual request patterns and implementing robust incident response plans will help detect and mitigate potential exploitation attempts. Finally, organizations should conduct audits to identify any remaining systems running these outdated Apache versions and plan for their timely decommissioning or upgrade.