CVE-2026-119281

Summary

MariaDB Connector/J decodes every result as UTF-8 and guards
character_set_client against a change to another charset, but did not guard
character_set_results, and relied on the server's global
session_track_system_variables list to be told about charset changes at all.

Details

The connector learns about session variable changes through session tracking,
and closes the connection when character_set_client is switched away from UTF-8,
so that its UTF-8 decoding stays correct. Two gaps remained:

• character_set_results was not guarded: a server could switch it to another
  charset, after which the bytes of every result were decoded as UTF-8 although
  encoded otherwise.
• the list of tracked variables came from the server's global
  session_track_system_variables: a server configured, or made, not to track
  the character set variables could change them silently.

The fix requests an explicit session tracking list that includes both character
set variables whatever the server's global setting, and closes the connection
when character_set_results is changed to a charset other than utf8, utf8mb3
or utf8mb4, as it already did for character_set_client.

Impact

Integrity: a malicious or compromised server, or a MitM, can make the strings an
application reads differ from the bytes the server returned (inappropriate
encoding for the output context), which can defeat application-side validation
or escaping built on those values. Exploitation requires control of the server
side of the connection; no confidentiality or availability impact.

Credit

Reported by fg0x0