CVE-2021-22969
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 · uneditedConcrete CMS (formerly concrete5) versions below 8.5.7 has a SSRF mitigation bypass using DNS Rebind attack giving an attacker the ability to fetch cloud IAAS (ex AWS) IAM keys.To fix this Concrete CMS no longer allows downloads from the local network and specifies the validated IP when downloading rather than relying on DNS.Discoverer: Adrian Tiron from FORTBRIDGE ( https://www.fortbridge.co.uk/ )The Concrete CMS team gave this a CVSS 3.1 score of 3.5 AV:N/AC:H/PR:L/UI:N/S:C/C:L/I:N/A:N . Please note that Cloud IAAS provider mis-configurations are not Concrete CMS vulnerabilities. A mitigation for this vulnerability is to make sure that the IMDS configurations are according to a cloud provider's best practices.This fix is also in Concrete version 9.0.0
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 confidenceConcrete CMS versions below 8.5.7 contained an SSRF vulnerability that could be exploited via DNS Rebind attack. The application validated hostnames but not the resolved IP addresses, allowing attackers to bypass restrictions and access cloud IMDS endpoints to retrieve IAAS IAM credentials. The fix validates the actual IP address rather than relying on DNS resolution and blocks downloads from local/private network ranges.
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< 8.5.7CVSS 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
- Low
- Integrity
- None
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/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 checksWork through these to decide whether this CVE applies to you.
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Identify installed Concrete CMS versionAccess the dashboard and navigate to Dashboard > System & Settings > Overview, or check the version number in the footer of the admin pages. Alternatively, check the file /application/config/app.php for the version constant.Affected if The installed version is below 8.5.7 (for example, 8.5.6, 8.5.5, earlier 8.x releases, or any version prior to 8.5.7).
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Determine if external URL download feature is in useReview Concrete CMS usage for features that accept external URLs such as File Manager URL import, remote file downloads, thumbnail generation from external images, or any custom blocks that fetch content from remote URLs.Affected if The site uses any functionality that allows importing or downloading files from user-supplied URLs, as this is the attack vector for the SSRF vulnerability.
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Check if the site runs in a cloud environment with IMDSIdentify whether the web server hosting Concrete CMS runs on a cloud provider service such as AWS EC2, Azure VMs, Google Cloud Compute Engine, or other IaaS platforms that provide an Instance Metadata Service.Affected if The Concrete CMS server is hosted on a cloud IaaS platform with IMDS enabled and accessible from the application, as this enables credential theft via the SSRF.
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Verify IP validation is applied to URL requestsInspect the Concrete CMS source code, specifically the HTTP request handling classes or libraries used for external URL fetching. Look for validation logic that checks resolved IP addresses against private/local network ranges (such as 127.0.0.0/8, 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16).Affected if The application performs hostname validation only without checking the resolved IP address against private/network ranges, indicating the vulnerable code path is present.
A site is affected if it runs Concrete CMS version below 8.5.7, uses features that fetch external URLs, and is hosted in a cloud environment where IMDS is accessible from the application server.
Generated from the published advisory. Verify against your own configuration.
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 · scoped8.5.7
Update Concrete CMS to version 8.5.7 or 9.0.0 or later. Additionally, ensure cloud IMDS configurations follow provider best practices (e.g., disable IMDS or require hop limit on AWS to limit token retrieval attempts).
8.5.7 (or 9.0.0 for major version upgrade)
- Upgrade Concrete CMS to version 8.5.7 or higher (or to version 9.0.0 which also contains the fix)
- After upgrading, verify that external file download functionality works correctly and that local network requests are blocked
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation2.0 h
- Testing3.0 h
- Review / QA2.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2021-22969 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2021-22969 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- 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
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