Apache HTTP Server EUVD-2026-26944

Attacker must already possess authenticated write access to the web server file system with permissions to create or modify .htaccess files in a directory processed by Apache HTTP Server. This typically requires compromised FTP/SFTP credentials, shell access to the server, or exploitation of a separate web application vulnerability allowing arbitrary file writes. Additionally, the Apache configuration must have AllowOverride set to a permissive value (not None) for the target directory, enabling .htaccess processing. The vulnerability is limited to privilege escalation within the context of the httpd daemon user-attackers cannot directly escalate to root unless httpd itself runs with elevated privileges (which is non-standard). The CVSS network vector rating appears to assume the attacker can deliver the malicious .htaccess via a network-accessible mechanism, but the local author requirement significantly constrains the attack surface compared to unauthenticated remote exploitation. Exploitation complexity is low once file write access exists, requiring only knowledge of Apache module directive syntax and target file paths.

The CVSS 3.1 score of 8.8 (High) reflects the potential for complete confidentiality, integrity, and availability impact, but the attack vector classification appears inconsistent with the vulnerability description. CVSS indicates AV:N (Network) with PR:L (Low Privileges Required), yet the description specifies 'local .htaccess authors' which suggests the attacker must already have legitimate access to create or modify .htaccess files on the server-typically requiring shell access, FTP credentials, or a compromised web application with file write capabilities. This is more accurately characterized as a post-compromise privilege escalation rather than a remote network attack. The AC:L (Low Complexity) and UI:N (No User Interaction) ratings are consistent with automated exploitation once .htaccess write access exists. SSVC framework indicates no active exploitation (Exploitation: none) and non-automatable attack (Automatable: no), suggesting this requires attacker-specific configuration knowledge. Technical Impact is rated 'total' which aligns with the ability to read sensitive files like application configs, database credentials, or /etc/shadow if httpd runs with elevated permissions. Real-world risk is moderate: while the CVSS is high, exploitation requires pre-existing server access, limiting this to scenarios where shared hosting environments allow .htaccess modifications or where attackers have already compromised a web application. Priority should be high for shared hosting providers and environments where multiple users can deploy .htaccess files, but lower for single-tenant deployments with strict file system access controls.

An attacker with compromised credentials for a shared hosting account or a vulnerable web application with file upload capabilities writes a malicious .htaccess file to a directory under their control. The crafted .htaccess contains directives that exploit module interaction flaws to instruct the Apache httpd process to read sensitive files such as /var/www/config/database.php or /etc/httpd/conf/httpd.conf. When the attacker accesses a URL in that directory, Apache processes the malicious .htaccess file and returns the contents of the target file with httpd daemon privileges, exposing credentials or configuration secrets.