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Concrete CMS EUVD-2026-31359

| CVE-2026-8337 MEDIUM
Authorization Bypass Through User-Controlled Key (CWE-639)
2026-05-21 ConcreteCMS GHSA-8c7c-h7px-267g
6.3
CVSS 4.0
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CVSS VectorNVD

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/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
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
X

Lifecycle Timeline

1
Analysis Generated
May 21, 2026 - 22:45 vuln.today

DescriptionNVD

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

AnalysisAI

Insecure Direct Object Reference (IDOR) in Concrete CMS versions up to and including 9.5.0 enables unauthenticated remote attackers to cast fraudulent votes in restricted private surveys by submitting a private survey's optionID through the publicly accessible voting endpoint. The vulnerability is configuration-dependent - exploitation requires the target site to simultaneously host both public and private surveys - which the CVSS v4.0 vector encodes as AT:P (Attack Requirements: Present), moderately lowering the practical risk surface compared to a universally exploitable flaw. …

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EUVD-2026-31359 vulnerability details – vuln.today

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