In JForum 2.1.8, an unauthenticated, remote attacker can enumerate whether a user exists by using the "create user" function. If a register/check/username?username= request corresponds to a username that exists, then an "is already in use" error is produced. NOTE: this product is discontinued.
Severity
CVSS 3.0
5.3 medium
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
EPSS
1.8% chance of exploitation in the next 30 days; higher than 79% of CVEs (scores of 2026-10-31)