CVE-2017-17671: vBulletin

Critical severity, CVSS 9.8. EPSS: 3.1% chance of exploitation in the next 30 days.

vBulletin through 5.3.x on Windows allows remote PHP code execution because a require_once call is reachable with an unauthenticated request that can include directory traversal sequences to specify an arbitrary pathname, and because ../ traversal is blocked but ..\ traversal is not blocked. For example, an attacker can make an invalid HTTP request containing PHP code, and then make an index.php?routestring= request with enough instances of ".." to reach an Apache HTTP Server log file.

Affected products

• vBulletin vBulletin: from 5.0.1, up to and including 5.3.3; version 5.0.0 only

Published 2017-12-14. Last modified 2026-06-17.