CVE-2026-61511
CVE-2026-61511 is a critical-severity vulnerability with a CVSS 3.x base score of 9.8. Its EPSS exploit-prediction score of 71% places it in the 99th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-95.
Key facts
- Severity: Critical (CVSS 3.x base score 9.8)
- CVSS v4: 9.3
- EPSS exploit prediction: 71% (99th percentile)
- Actively exploited: Not listed in CISA KEV
- Weakness: CWE-95
- Published:
- Last modified:
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.
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.
- How severe is CVE-2026-61511?
- CVE-2026-61511 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
- Is CVE-2026-61511 being actively exploited?
- It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 71% (99th percentile), an estimate of the probability of exploitation in the next 30 days.
- How do I fix CVE-2026-61511?
- Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
- When was CVE-2026-61511 published?
- CVE-2026-61511 was published on 2026-07-27 and last updated on 2026-08-07.
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
- http://seclists.org/fulldisclosure/2026/Aug/29
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