Page History

...

Suppose a system authenticates users by issuing the following query to a SQL database. If the query returns any results, authentication succeeds; otherwise, authentication fails.

SELECT * FROM db_user WHERE username='<USERNAME>' AND 
                            password='<PASSWORD>'

Suppose an attacker can substitute arbitrary strings for <USERNAME> and <PASSWORD>. In that case, the authentication mechanism can be bypassed by supplying the following <USERNAME> with an arbitrary password:

validuser' OR '1'='1

The authentication routine dynamically constructs the following query:

SELECT * FROM db_user WHERE username='validuser' OR '1'='1' AND password='<PASSWORD>'

...

Similarly, an attacker could supply the following string for <PASSWORD> with an arbitrary username:

' OR '1'='1

producing the following query:

SELECT * FROM db_user WHERE username='<USERNAME>' AND password='' OR '1'='1'

...

Failure to sanitize user input before processing or storing it can result in injection attacks.

Automated Detection

Related Vulnerabilities

CVE-2008-2370 describes a vulnerability in Apache Tomcat 4.1.0 through 4.1.37, 5.5.0 through 5.5.26, and 6.0.0 through 6.0.16. When a RequestDispatcher is used, Tomcat performs path normalization before removing the query string from the URI, which allows remote attackers to conduct directory traversal attacks and read arbitrary files via a .. (dot dot) in a request parameter.

...

...