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Concrete CmsApplication · Concretecms

CVE-2026-8337

MEDIUM · 5.3 CVSS v3.1 Published 2026-05-21
Fix available
A fix is available. Upgrade to 9.5.1 or later.
See remediation →
62/100
Remediation priority · Elevated
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

IDOR vulnerability in Concrete CMS surveys allows unauthenticated attackers to vote in restricted (private) surveys by submitting the restricted optionID through the public survey endpoint. The attack requires the site to have both public and private surveys configured.

MitigationUpdate Concrete CMS to a version above 9.5.0 when available, or implement proper access control validation on survey endpoints to ensure users can only vote in surveys they are authorized to access.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Concrete CmsApplication
Affected:< 9.5.1

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify installed Concrete CMS version
    Log into the dashboard and navigate to Dashboard > System & Settings > Basics > Maintenance Mode, or check the composer.json file in the installation root for the 'concrete5' or 'concretecms' version entry
    Affected if The installed version is lower than 9.5.1 (e.g., 9.5.0, 9.4.x, 9.x.x, or any version below 9.5.1)
  2. Confirm survey functionality is enabled
    Navigate to Dashboard > Pages & Themes > Search for 'survey' in the add functionality area, or check the database table 'Packages' for an entry where packageID corresponds to the survey package (typically 'core_commerce' or custom survey package)
    Affected if The survey feature or survey-related package is installed and active
  3. Identify active surveys in the system
    Query the database for survey blocks: look in tables like 'Blocks' where blockTypeHandle contains 'survey' or 'poll', or navigate to any page known to contain a survey and inspect the survey block configuration
    Affected if One or more surveys exist in the system, particularly surveys with restricted/private options configured
  4. Check survey voting endpoint accessibility
    Inspect the survey block's form action URL (typically /index.php/tools/required/surveys/vote or similar endpoint) and verify if it accepts an optionID parameter without additional authorization token validation
    Affected if The survey voting endpoint accepts direct optionID submission without verifying that the user has permission to vote on the specific survey associated with that optionID

A system is affected if it runs Concrete CMS version below 9.5.1 and has active surveys with restricted/private options, where the voting endpoint does not validate that the submitted optionID belongs to a survey the user is authorized to vote on.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 9.5.1 or later
Fixed in 9.5.1
Interim mitigation

Update Concrete CMS to a version above 9.5.0 when available, or implement proper access control validation on survey endpoints to ensure users can only vote in surveys they are authorized to access.

Recommended fix High confidence

9.5.1 or later

  1. 1. Back up your Concrete CMS database and files before starting the upgrade process
  2. 2. Download Concrete CMS version 9.5.1 or later from the official source (documentation.concretecms.org)
  3. 3. Extract the new version files to your web server
  4. 4. Run the update process by navigating to /ccm/system/upgrade or using the concrete CLI tool
  5. 5. Verify the upgrade was successful by logging into the dashboard
  6. 6. Confirm the survey functionality works correctly with both public and private surveys

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Concrete Cms Scoped from the published advisory
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
12.0 hours of engineering $2,130
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,408.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-8337 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data