What is CVE-2026-61511?A critical-severity flaw, explained.
CVE-2026-61511 is a critical-severity flaw (CVSS 9.3) in the software it affects, published on 27 July 2026. It is not on the list of flaws known to be exploited today. The latest forecast puts its chance of use in the next 30 days at 74%. If you run an affected version, plan in the vendor’s fix.
Published 27 July 2026. Record last updated 3 November 2026. We keep this page's data up to date.
What is CVE-2026-61511? In plain terms.
It can be attacked from anywhere on the internet without logging in, and nobody has to click anything.
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.
What kind of flaw is it?
- CWE-95Improper Neutralization of Directives in Dynamically Evaluated Code ('Eval Injection')
How an attack on it works
Read straight from its severity rating, translated out of the shorthand.
- Where an attacker can beAnywhere on the internet
- How hard it is to pull offEasy: no special conditions
- Login needed firstNo login needed
- Does someone have to clickNo, nobody has to do anything
Severity vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Is CVE-2026-61511 being exploited? Not that we know of.
It is not on the list of flaws known to be exploited today. The latest forecast puts the chance of it being used in the next 30 days at 74%. That can change at any time, which is why we keep watching.
Timeline
- Published
- Exploit likelihood jumped
- Exploit likelihood fell
- Record last updated
CVE-2026-61511 scores 71. Action: Patch now.
We keep the score of every published flaw up to date as the evidence changes. Four things go into the score, and evidence that criminals are actually using it counts most. In order:
- Evidence it is being exploitedBiggest factor
- How severe it isStrong factor
- How widely exposed it isKey context
- Real threat activity around itKey context
85 and above is Critical. Anything confirmed as exploited is always marked for an emergency patch, whatever its score.
When CVE-2026-61511 matches software you track, it lands in your list with its score and the reasons behind it.
See your own ranked list →Who is affected by CVE-2026-61511? 0 products.
Here is what the published record lists as affected.
No affected products have been listed for this flaw yet. That usually means the record is still being analysed.
How do I fix CVE-2026-61511? Four steps.
- Check whether you run itCompare your versions with the affected products above. Not sure what you run? EdgeProtect can work it out from your public website, or you can pick it from a list.
- Apply the vendor’s fixInstall the latest update from the vendor. The references list where the vendor has published details.
- If you can’t patch todayFollow any mitigation the vendor publishes, and limit who can reach the affected system from the internet until the update is in.
- Keep an eye on itTrack the product and we tell you as soon as we spot this flaw on the list of exploited flaws, or a jump in its exploit likelihood.
References
6 links- Security Patch Released for Vbulletin 6 2 1 6 2 0 and 6 1 6 (opens in a new tab)vbulletin.com
- Vbulletin 6 2 2 Is Available (opens in a new tab)vbulletin.com
- Web page (opens in a new tab)karmainsecurity.com · 2026
- Vbulletin Runtime Template Runmaths Preauth RCE (opens in a new tab)ssd-disclosure.com
- Vbulletin Eval Injection RCE via Vb5 Template Runtime Php (opens in a new tab)vulncheck.com
- Fulldisclosure (opens in a new tab)seclists.org · 2026
Does CVE-2026-61511 affect you? We'll keep checking.
Looking flaws up one at a time doesn't scale. Tell us what you run once, and we tell you which flaws matter to you, in what order, and keep watching for new ones.
- Tell us what you runPick your software from a list, or let us work it out from your website.
- We match it to every flawOver 400,000 published flaws, checked against your list.
- Ranked by real-world riskA 0 to 100 score, led by evidence criminals are using it.
- Told as soon as we knowAn alert by email, in the app or by webhook to your own tools.
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1 new flaw affects software Acme tracks
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...
- Matched to
- Your software on Acme's software list
- What to do
- Plan in the vendor’s update
Sent to the alert recipients Acme chose. Also in the app and to Acme's webhook.
CVE-2026-61511 is a critical-severity flaw in the software it affects, published on 27 July 2026. It can be attacked from anywhere on the internet without logging in, and nobody has to click anything.
It scores 9.3 out of 10 on the CVSS severity scale, which is critical. Our risk score for CVE-2026-61511 is 71 out of 100, which is High. Its action is "Patch now". Not confirmed as exploited yet, but serious or likely enough that it should not wait for a quiet month.
It is not on the list of flaws known to be exploited today. The latest forecast puts the chance of it being used in the next 30 days at 74%. That can change at any time, which is why we keep watching.
Install the update the vendor names in its advisory. If you can't patch today, follow the vendor's mitigation and limit who can reach the affected system from the internet.