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.
Attack Parameters
Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Attack Requirements
None
No additional conditions
Privileges Required
None
No privileges needed
User Interaction
None
No user interaction needed
Impact Assessment
Confidentiality
High
Complete data leak
Integrity
High
Complete data modification
Availability
High
Complete denial of service
CVSS Vector v4.0
Weakness Type (CWE)
Vulnerable Products
vbulletin:vbulletin
References 5
https://forum.vbulletin.com/forum/vbulletin-announcements/vbulletin-announcemen…
disclosure@vulncheck.com
https://forum.vbulletin.com/forum/vbulletin-announcements/vbulletin-announcemen…
disclosure@vulncheck.com
https://karmainsecurity.com/KIS-2026-13
disclosure@vulncheck.com
https://ssd-disclosure.com/vbulletin-runtime-template-runmaths-preauth-rce/
disclosure@vulncheck.com
https://www.vulncheck.com/advisories/vbulletin-eval-injection-rce-via-vb5-templ…
disclosure@vulncheck.com