dbcve.org
Concrete CmsApplication · Concretecms

CVE-2021-22958

CRITICAL · 9.8 CVSS v3.1 Published 2021-10-07
Fix available
A fix is available. Upgrade to 8.5.5 or later.
See remediation →
100/100
Remediation priority · Urgent
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
A Server-Side Request Forgery vulnerability was found in concrete5 < 8.5.5 that allowed a decimal notation encoded IP address to bypass the limitations in place for localhost allowing interaction with local services. Impact can vary depending on services exposed.CVSSv2.0 AV:A/AC:H/PR:H/UI:N/S:U/C:L/I:N/A:N

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

A Server-Side Request Forgery (SSRF) vulnerability in concrete5 versions before 8.5.5 allows attackers to bypass localhost restrictions by using decimal notation encoded IP addresses (e.g., 127.0.0.1 converts to 2130706433), enabling interaction with internal services that should be protected by network restrictions.

MitigationUpgrade concrete5 to version 8.5.5 or later, which includes proper input validation to prevent decimal notation IP address bypasses.

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
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

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

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. Determine the installed concrete5 version
    Log in to the concrete5 dashboard and navigate to Dashboard > System & Settings > About, or check the version.php file in the /application/config/ or /concrete/ directory
    Affected if The installed version is any release before 8.5.5 (e.g., 8.5.4, 8.5.3, earlier versions)
  2. Identify if external URL requests are accepted
    Locate any forms, API endpoints, or features in the concrete5 site that accept URL input from users, such as file import from URL, webhooks, or content scraping features
    Affected if The site has functionality that allows users to submit or specify URLs that the server will fetch or request
  3. Test decimal IP address handling
    If URL input functionality exists, submit a request using decimal IP notation (e.g., http://2130706433/ or http://3232235777/) instead of localhost or 127.0.0.1 to see if the application accepts it
    Affected if The application accepts URLs with decimal-encoded IP addresses and processes the request, indicating the validation bypass is present

You are affected if your concrete5 installation is version 8.5.4 or earlier AND your site has features that accept URL input from users, allowing potential SSRF attacks via decimal IP notation bypass.

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 8.5.5 or later
Fixed in 8.5.5
Interim mitigation

Upgrade concrete5 to version 8.5.5 or later, which includes proper input validation to prevent decimal notation IP address bypasses.

Recommended fix High confidence

Concrete CMS 8.5.5 or later

  1. 1. Create a complete backup of the database and all site files
  2. 2. Download Concrete CMS version 8.5.5 or later from the official Concrete CMS repository (https://www.concretecms.com/download)
  3. 3. Extract the new version files
  4. 4. Upload the new files to your server, overwriting the existing installation
  5. 5. Run the upgrade process by accessing your site URL - the system will automatically detect and apply updates
  6. 6. Clear any caching mechanisms (application cache, opcode cache, CDN cache)
  7. 7. Verify the installation by logging into the dashboard and confirming version number
  8. 8. Test that external requests work properly and the SSRF protection correctly blocks malicious requests
Caveat Review the Concrete CMS 8.5.5 release notes for any breaking changes between your current version and 8.5.5 before upgrading

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.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2021-22958 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

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-2021-22958 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

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