(select concat(0x3a,char(64),char(52),char(51),char(55),char(48),char(49),(SELECT super_priv FROM mysql.user WHERE user=(SELECT user) LIMIT…

Here’s what that expression is doing, in plain terms, and what it would produce in a MySQL context.

What the code does

• It uses MySQL’s CONCAT function to build a single string.
• It pieces together several ASCII/character literals:
  • 0x3a is ":" (a hex literal)
  • char(64) is "@"
  • char(52), char(51), char(55), char(48), char(49) are the digits "43701"
• It then inserts the value returned by a subquery:
  • (SELECT super_priv FROM mysql.user WHERE user=(SELECT user) LIMIT 1)
    • This fetches the SUPER privilege flag (usually 'Y' or 'N', sometimes NULL) for the current user, determined by (SELECT user).
• After that, it adds another "@" and the digits:
  • char(64) -> "@"
  • char(49), char(48), char(55), char(51), char(52) -> "10734"

Put together, the final string has the form: : @ 43701 @ 10734 without the spaces: :@43701@10734

What the final string would look like

• If the current user’s super_priv is 'Y', the result would be: :@43701Y@10734
• If it’s 'N', the result would be: :@43701N@10734
• If the subquery returns NULL (e.g., no matching row), you’d get: :@43701NULL@10734

Why this exists (educational context)

• It’s a payload pattern often seen in SQL injection scenarios to exfiltrate data:
  • It obfuscates parts of the payload using ASCII codes.
  • It reads a privileged column (super_priv) from the mysql.user table for the current user.
  • It formats the result in a predictable string, usually for easy detection/automation.

Security and defensive notes

• Accessing mysql.user and reading super_priv requires appropriate privileges. A vulnerable application would need an injection flaw for this payload to run.
• Mitigations include:
  • Use least-privilege database accounts (no broad access to mysql.* for app users).
  • Disable or tightly restrict direct SELECT access to the mysql database.
  • Use prepared statements/parameterized queries and input validation to prevent SQL injection.
  • Employ a WAF and code reviews to catch such obfuscated payloads.
  • Regularly patch and audit MySQL configurations and user privileges.

If you’re studying for an exam, you can use this to illustrate:

• How CONCAT and char(...) can be used to assemble strings.
• How nested SELECTs can pull data from system tables.
• How payloads might be obfuscated (e.g., using hex literals) to bypass simple filters.

If you want, I can provide a safe, fully contained example with a mock table and show exactly what the output would be given different mock super_priv values.