CVE-2024-38475 is a critical security vulnerability identified in the Apache HTTP Server, specifically affecting versions 2.4.0 through 2.4.59. The issue stems from improper encoding or escaping of output in the mod_rewrite module, which is widely used to rewrite requested URLs on the server side. The vulnerability occurs when substitutions in the server context use backreferences or variables as the first segment of the substitution path. Due to insufficient escaping, attackers can craft malicious URLs that map to filesystem locations which are normally not directly reachable via any URL. This can lead to unauthorized access to sensitive files, including source code disclosure, or even remote code execution if executable files are exposed. The rewrite flag "UnsafePrefixStat" can be used to revert to previous behavior but requires careful constraint of substitutions to avoid exploitation. The vulnerability does not require any authentication or user interaction and can be exploited remotely over the network, making it highly dangerous. The CVSS 3.1 base score of 9.1 reflects the critical nature of this flaw, with high impact on confidentiality and integrity and low attack complexity. No public exploits have been reported yet, but the vulnerability is publicly disclosed and should be addressed promptly.

For European organizations, the impact of CVE-2024-38475 can be significant. Apache HTTP Server is widely deployed across Europe in government, financial institutions, healthcare, and enterprise environments. Exploitation could lead to unauthorized disclosure of sensitive data, including source code or configuration files, which may contain credentials or business logic. In worst cases, attackers could achieve remote code execution, compromising the entire server and potentially pivoting to internal networks. This could disrupt critical services, lead to data breaches, and cause reputational damage. Organizations with complex URL rewriting rules or legacy Apache configurations are particularly vulnerable. The lack of authentication or user interaction requirements means attackers can exploit this remotely and anonymously, increasing the risk of widespread attacks. Additionally, the vulnerability could be leveraged in targeted attacks against high-value European targets, including government and infrastructure sectors.

To mitigate CVE-2024-38475, European organizations should immediately upgrade Apache HTTP Server to a version later than 2.4.59 once patches are released. Until then, administrators should audit and review all mod_rewrite rules, especially those using backreferences or variables as the first segment in substitutions. Avoid using unsafe RewriteRules and consider disabling or restricting mod_rewrite functionality where possible. If the "UnsafePrefixStat" flag is used, ensure that substitutions are tightly constrained and validated to prevent exploitation. Implement strict access controls on filesystem locations to prevent unintended exposure. Employ web application firewalls (WAFs) with rules designed to detect and block suspicious URL patterns targeting mod_rewrite. Regularly monitor server logs for anomalous requests that could indicate exploitation attempts. Finally, maintain a robust incident response plan to quickly address any detected compromises.