CVE-2024-38477 is a vulnerability identified in the Apache HTTP Server, specifically affecting the mod_proxy module in versions up to 2.4.59. The root cause is a NULL pointer dereference (CWE-476), which occurs when the server processes a maliciously crafted request. This dereference leads to a crash of the Apache HTTP Server process, resulting in a denial-of-service (DoS) condition. The vulnerability can be exploited remotely without any authentication or user interaction, making it relatively easy for attackers to trigger. The Common Vulnerability Scoring System (CVSS) v3.1 rates this vulnerability at 7.5 (high severity), reflecting its network attack vector, low attack complexity, and no privileges or user interaction required. The impact is limited to availability, with no direct compromise of confidentiality or integrity. The Apache Software Foundation has addressed this issue in version 2.4.60, and users are urged to upgrade to mitigate the risk. Although no exploits have been reported in the wild yet, the simplicity of triggering the crash makes it a significant threat, especially for public-facing web servers that utilize mod_proxy for reverse proxy or load balancing functions. Organizations running vulnerable versions should prioritize patching and consider additional monitoring of proxy traffic to detect potential exploitation attempts.

For European organizations, the primary impact of CVE-2024-38477 is the potential for denial-of-service attacks against web servers running Apache HTTP Server with mod_proxy enabled. This can lead to service outages, affecting business continuity, customer access, and potentially causing reputational damage. Critical sectors such as finance, government, healthcare, and telecommunications that rely heavily on Apache HTTP Server for web services may experience operational disruptions. The vulnerability does not allow data theft or modification but can be used as a vector for broader attacks by causing downtime or distracting security teams. Given the widespread use of Apache HTTP Server across Europe, unpatched systems could be targeted by opportunistic attackers or incorporated into larger attack campaigns. The lack of known exploits in the wild currently reduces immediate risk, but the ease of exploitation means the threat could escalate rapidly if weaponized.

1. Upgrade Apache HTTP Server to version 2.4.60 or later immediately to apply the official patch fixing the NULL pointer dereference. 2. If immediate patching is not feasible, consider temporarily disabling or restricting access to the mod_proxy module, especially on public-facing servers. 3. Implement network-level protections such as Web Application Firewalls (WAFs) to detect and block malformed or suspicious proxy requests targeting mod_proxy. 4. Monitor server logs and proxy traffic for unusual request patterns that could indicate exploitation attempts. 5. Employ rate limiting on proxy endpoints to reduce the risk of DoS attacks. 6. Conduct regular vulnerability scans and penetration tests focusing on Apache HTTP Server configurations. 7. Ensure incident response plans include procedures for handling DoS attacks and rapid patch deployment. 8. Educate system administrators about this vulnerability and the importance of timely updates.