CVE-2025-54090 is a vulnerability identified in Apache HTTP Server version 2.4.64, categorized under CWE-253 (Incorrect Check of Function Return Value). The flaw causes all conditional expressions within the "RewriteCond expr ..." directive to evaluate as true regardless of their actual logic. This occurs because the server incorrectly processes the return values of functions used in these rewrite conditions, leading to unintended behavior in URL rewriting rules. Since Apache HTTP Server is widely used to manage web traffic and enforce access controls via rewrite rules, this bug can cause security policies to be bypassed or misapplied. For example, rewrite conditions intended to restrict access or redirect requests based on specific criteria may fail, allowing unauthorized access or exposure of sensitive resources. The vulnerability requires an attacker to have network access to the affected server and low privileges (e.g., ability to send crafted HTTP requests), but no user interaction is necessary. The CVSS v3.1 base score is 6.3 (medium), reflecting the moderate impact on confidentiality, integrity, and availability, combined with relatively low attack complexity and no need for user interaction. The issue was publicly disclosed on July 23, 2025, with no known exploits in the wild at the time of publication. The Apache Software Foundation addressed the vulnerability in version 2.4.65, and users are strongly advised to upgrade to this version to remediate the issue.

For European organizations, the vulnerability poses a risk to web servers running Apache HTTP Server 2.4.64, which is common in enterprise, government, and service provider environments. The incorrect evaluation of rewrite conditions can lead to unauthorized access to protected resources, bypass of security controls, or unintended request routing. This can compromise confidentiality by exposing sensitive data, integrity by allowing unauthorized modifications or access, and availability by enabling denial-of-service scenarios through misrouted or malformed requests. Organizations relying on Apache for critical web applications, especially those handling personal data under GDPR, face increased compliance and reputational risks if exploited. The medium severity indicates that while the vulnerability is not trivially exploitable for full system compromise, it can facilitate lateral movement or privilege escalation when combined with other weaknesses. The absence of known exploits reduces immediate urgency but does not eliminate the threat, as attackers may develop exploits given the public disclosure.

European organizations should immediately upgrade all Apache HTTP Server instances from version 2.4.64 to 2.4.65 or later to eliminate the vulnerability. In environments where immediate upgrade is not feasible, administrators should audit and review all "RewriteCond expr ..." directives to identify and temporarily disable or tighten rules that could be exploited due to the incorrect evaluation. Implementing strict access controls and network segmentation can limit exposure of vulnerable servers. Monitoring web server logs for unusual rewrite behavior or unexpected access patterns can help detect exploitation attempts. Additionally, organizations should ensure that their incident response plans include scenarios involving web server misconfigurations and maintain up-to-date backups to recover from potential availability impacts. Coordinating with Apache support channels and subscribing to security advisories will help stay informed about any emerging exploits or patches.