{keyword}) Union All Select Null,null,null,null,null,null# Apr 2026
: This is a common reconnaissance technique. An attacker uses NULL values to determine the exact number of columns returned by the original query. If the number of NULL s doesn't match the original column count, the database will usually throw an error. By adding or removing NULL s, an attacker can find the correct structure.
To protect your application from this type of attack, you should avoid building queries using simple string concatenation. Instead, use: {KEYWORD}) UNION ALL SELECT NULL,NULL,NULL,NULL,NULL,NULL#
: This is the core of the attack. The UNION operator combines the results of two or more SELECT statements into a single result set. ALL ensures that duplicate rows are kept. : This is a common reconnaissance technique
: Only allow expected characters and formats. By adding or removing NULL s, an attacker
If this payload successfully returns a blank page instead of an error, it confirms to a tester that the application is vulnerable. From there, they can replace the NULL s with commands to extract sensitive data, such as: Usernames and passwords. Database version and configuration details. The entire contents of specific tables. How to Prevent It
