CVE-2011-2688 in Mod Authnz External
Summary
by MITRE
SQL injection vulnerability in mysql/mysql-auth.pl in the mod_authnz_external module 3.2.5 and earlier for the Apache HTTP Server allows remote attackers to execute arbitrary SQL commands via the user field.
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Analysis
by VulDB Data Team • 11/15/2021
The vulnerability identified as CVE-2011-2688 represents a critical SQL injection flaw within the mod_authnz_external module version 3.2.5 and earlier for the Apache HTTP Server. This issue affects the mysql/mysql-auth.pl script component that handles external authentication mechanisms, creating a pathway for malicious actors to exploit the authentication system. The vulnerability specifically targets the user field parameter, which is processed without adequate input sanitization, allowing attackers to inject malicious SQL commands directly into the authentication flow.
The technical exploitation of this vulnerability occurs through the improper handling of user input in the authentication script. When a user attempts to authenticate through the Apache server using mod_authnz_external, the system processes the provided username in a manner that does not properly escape or validate special SQL characters. This design flaw enables attackers to craft malicious input that gets directly incorporated into SQL queries executed against backend MySQL databases. The vulnerability falls under CWE-89 which specifically addresses SQL injection weaknesses, where insufficient input validation allows attackers to manipulate database queries through user-controllable parameters. The attack vector is particularly dangerous because it operates at the authentication layer, potentially providing attackers with elevated privileges or unauthorized database access.
The operational impact of this vulnerability extends beyond simple unauthorized access, as it can enable comprehensive database compromise and privilege escalation within the affected environment. An attacker who successfully exploits this vulnerability can execute arbitrary SQL commands against the MySQL database, potentially leading to data exfiltration, data manipulation, or complete database compromise. The authentication bypass capability means that malicious actors could gain access to protected resources without proper authorization, while the SQL injection component allows for deeper system penetration. This vulnerability aligns with ATT&CK technique T1190 which covers exploitation of remote services through injection attacks, and T1078 which covers valid accounts usage for persistence and privilege escalation.
Mitigation strategies for CVE-2011-2688 require immediate action to address the core authentication module vulnerability. The primary recommendation involves upgrading the mod_authnz_external module to version 3.2.6 or later, where the SQL injection flaw has been patched and proper input validation has been implemented. Organizations should also implement proper input sanitization measures at the application level, ensuring that all user-controllable parameters are properly escaped before database interaction. Network segmentation and firewall rules should be implemented to restrict access to the authentication endpoints, while database access controls should be tightened to limit the privileges of the authentication service account. Additionally, comprehensive logging and monitoring should be enabled to detect anomalous authentication patterns that might indicate exploitation attempts, and regular security assessments should be conducted to identify similar vulnerabilities in other authentication modules and web applications.