What is CVE-2026-8337?

CVE-2026-8337 is a medium-severity vulnerability in Concrete Cms, classified under Reliance on Cookies without Validation and Integrity Checking. CVSS score: 5.3/10. Published 2026-05-21.

How severe is CVE-2026-8337?

Medium severity. CVSS v3 base score is 5.3 out of 10.

Is CVE-2026-8337 known to be exploited?

1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

Auth bypass in Concrete Cms

CVE-2026-8337

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

EPSS: 0.002 (9.1th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N.

Affected products

Concrete Cms — versions 5.0
Concretecms Concrete_cms

Weakness classification (CWE)

Public proof-of-concept exploits

aj2108/CVE-2026-8337

References

ff5b8ace-8b95-4078-9743-eac1ca5451de (release-notes, Release Notes)

Frequently asked questions

What is CVE-2026-8337?: CVE-2026-8337 is a medium-severity vulnerability in Concrete Cms, classified under Reliance on Cookies without Validation and Integrity Checking. CVSS score: 5.3/10. Published 2026-05-21.
How severe is CVE-2026-8337?: Medium severity. CVSS v3 base score is 5.3 out of 10.
Is CVE-2026-8337 known to be exploited?: 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.