vBulletin 5.x through 5.1.6 allows remote authenticated users to bypass authorization checks and inject private messages into conversations via vectors related to an input validation failure.
Severity
CVSS 3.0
6.5 medium
CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
EPSS
1.0% chance of exploitation in the next 30 days; higher than 62% of CVEs (scores of 2026-10-31)