CVE-2026-8337Network attack vector

Unauthorized survey voting via unchecked option identifier

Published May 21, 2026 · Updated May 21, 2026

Authorization bypass in Concrete CMS 5.0 through 9.5.0 allows remote attackers to cast votes in restricted surveys through a public endpoint. The survey vote handler accepts a user-controlled optionID from a public survey request without verifying that the option belongs to that publicly accessible survey. Exploitation requires public and private surveys on the same site, and the bounded consequence is unauthorized modification of private survey vote totals.

CVSS severity6.3
Medium
EPSS probability0.19%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Authorization bypass in Concrete CMS 5.0 through 9.5.0 allows remote attackers to cast votes in restricted surveys through a public endpoint. The survey vote handler accepts a user-controlled optionID from a public survey request without verifying that the option belongs to that publicly accessible survey. Exploitation requires public and private surveys on the same site, and the bounded consequence is unauthorized modification of private survey vote totals.

The record

CVE
CVE-2026-8337
Published
May 21, 2026
Updated
May 21, 2026
Vendor
Concrete CMS
Product
Concrete CMS
Classifications
CWE-639, CWE-565, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 21, 2026CVE publishedPublication date reported by the CVE source.
  2. May 21, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=5.0 <=9.5.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Concrete CMS · Concrete CMSversion=5.0 <=9.5.0

Published CVSS scores

5.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
6.3ConcreteCMSCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-639Authorization Bypass Through User-Controlled Key
CWE-565Reliance on Cookies without Validation and Integrity Checking
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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