Vulnerability · Published May 21, 2026 · Assigned by ConcreteCMS
CVE-2026-8337Concrete CMS 9.5.0 and below is vulnerable to IDOR in surveys when sites are running concurrent public surveys and private surveys
Medium 6.3
In plain English
A medium-severity authorization bypass via user-controlled key in Concrete CMS from Concrete CMS. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 9% of all known vulnerabilities). Ready-made attack tooling exists: public proof-of-concept code. Fixed versions are available - upgrade the affected package.
Official description
Concrete CMS 9.5.0 and below is vulnerable to IDOR in surveys. To be vulnerable, a site would have to be configured in such a way that both public and private surveys are present on the site. An unauthenticated attacker can vote in the restricted survey by submitting the restricted optionID through the public survey’s endpoint. The Concrete CMS security team gave this vulnerability a CVSS v.4.0 score of 6.3 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N. Thanks Zer0daySec https://github.com/Zee99y for reporting
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Packagist | concrete5/concrete5 | 9.5.1 | GHSA-8c7c-h7px-267g |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Concrete CMS | Concrete CMS | 5.0 – through 9.5.0 |
Weakness: CWE-639, CWE-565 · Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N