SQL injection vulnerability in mod_auth_mysql.c in the mod-auth-mysql (aka libapache2-mod-auth-mysql) module for the Apache HTTP Server 2.x, when configured to use a multibyte character set that allows a \ (backslash) as part of the character encoding, allows remote attackers to execute arbitrary SQL commands via unspecified inputs in a login request.
The product constructs all or part of an SQL command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended SQL command when it is sent to a downstream component. Without sufficient removal or quoting of SQL syntax in user-controllable inputs, the generated SQL query can cause those inputs to be interpreted as SQL instead of ordinary user data.