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Concrete CmsApplication · Concretecms

CVE-2021-28145

MEDIUM · 5.4 CVSS v3.1 Published 2021-03-18
Fix available
A fix is available. Upgrade to 8.5.5 or later.
See remediation →
58/100
Remediation priority · Elevated
Remotely reachable

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 (formerly concrete5) before 8.5.5 allows remote authenticated users to conduct XSS attacks via a crafted survey block. This requires at least Editor privileges.

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

Concrete CMS versions prior to 8.5.5 contain a stored Cross-Site Scripting (XSS) vulnerability in the survey block functionality. Authenticated users with Editor-level privileges or higher can inject malicious JavaScript code through crafted survey block submissions, which then executes when other users view the affected content.

MitigationUpgrade Concrete CMS to version 8.5.5 or later to obtain the security patch. Alternatively, restrict Editor-level privileges pending the upgrade.

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:< 8.5.5

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
Low
User interaction
Required
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/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. Check installed Concrete CMS version
    Log into the CMS dashboard and navigate to Dashboard > System & Settings > Basics > Application Dashboard, or check the file /application/config/app.php for the version number
    Affected if The version displayed is below 8.5.5 (for example 8.5.4, 8.5.3, 8.5.2, etc.)
  2. Verify survey block usage
    Navigate to Pages & Themes > Full Sitemap and inspect pages for survey blocks, or check the database table btSurvey for any entries
    Affected if Any survey blocks exist in the system and the CMS version is below 8.5.5
  3. Check user privilege levels
    Review the CMS user groups in Dashboard > Users > User Groups, focusing on accounts with Editor-level access
    Affected if There are users assigned Editor-level or higher privileges who have access to add or edit survey blocks

A user is affected if their Concrete CMS installation is version 8.5.4 or lower AND the survey block feature is enabled or has been used on any page.

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.

From vendor data
Upgrade available Upgrade to 8.5.5 or later
Fixed in 8.5.5
Interim mitigation

Upgrade Concrete CMS to version 8.5.5 or later to obtain the security patch. Alternatively, restrict Editor-level privileges pending the upgrade.

Fix this in Concrete Cms Scoped from the published advisory
  • Consultation2.0 h
  • Implementation3.0 h
  • Testing2.0 h
  • Review / QA1.0 h
8.0 hours of engineering $1,420
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,272.

Scan for this in your stack

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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-2021-28145 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