CVE-2026-61511: vBulletin

Critical severity, CVSS 9.8. EPSS: 5.6% chance of exploitation in the next 30 days.

vBulletin 5.x through 5.7.5 and 6.x through 6.2.1 contains an eval injection vulnerability in the vB5_Template_Runtime::runMaths() method within the template runtime that allows unauthenticated remote attackers to execute arbitrary PHP code by supplying crafted input through the pagenav[pagenumber] parameter. Attackers can exploit the insufficiently restrictive regex filter by using phpfuck-style encoding with permitted characters to inject and execute arbitrary PHP code via the unauthenticated ajax/render template route without any authentication.

Affected products

• vBulletin vBulletin: from 5.0.0, up to and including 5.7.5; from 6.0.0, up to and including 6.2.1

Published 2026-07-27. Last modified 2026-08-07.