CVE-2026-61511: Code Injection (CVSS 9.8)

Description

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.

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CVSS v3.1 Score

9.8

CRITICAL

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS — Exploit Prediction

0.0127

Probability of exploitation

0.67%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-95 CWE-95

References

Other References

https://forum.vbulletin.com/forum/vbulletin-announcements/vbulletin-announcements_aa/4509358-security-patch-released-for-vbulletin-6-2-1-6-2-0-and-6-1-6 https://forum.vbulletin.com/forum/vbulletin-announcements/vbulletin-announcements_aa/4509404-vbulletin-6-2-2-is-available https://karmainsecurity.com/KIS-2026-13 https://ssd-disclosure.com/vbulletin-runtime-template-runmaths-preauth-rce/ https://www.vulncheck.com/advisories/vbulletin-eval-injection-rce-via-vb5-template-runtime-php

Frequently Asked Questions

What is CVE-2026-61511? +

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. It has a CVSS v3.1 base score of 9.8 (CRITICAL).

How severe is CVE-2026-61511? +

CVE-2026-61511 has a CVSS v3.1 score of 9.8 out of 10, rated CRITICAL. This is a critical vulnerability that should be patched immediately. The EPSS score is 0.0127, placing it in the 1th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-61511? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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