CVE-2026-8139
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 9.5.0 and below is vulnerable to Stored XSS via external-link page cvName because updateCollectionAliasExternal bypasses being sanitized. The Concrete CMS security team gave this vulnerability a CVSS v.4.0 score of 2.0 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:P/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N. Thanks Yonatan Drori (Tenzai) 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 confidenceConcrete CMS 9.5.0 and below contains a Stored XSS vulnerability in the external-link page functionality. The updateCollectionAliasExternal function fails to properly sanitize the cvName parameter, allowing authenticated attackers with high privileges to inject malicious scripts that persist in the application.
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<= 9.5.0CVSS 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 checksWork through these to decide whether this CVE applies to you.
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Check Concrete CMS versionLocate the version file or dashboard version info (typically in /application/config/version.php or via admin dashboard/system information). Compare the installed version to the affected range: any version <= 9.5.0 is vulnerable.Affected if Installed version is 9.5.0 or lower
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Identify external link pagesQuery the database or navigate the CMS admin panel to list pages of type 'external link' or alias pages. Look for pages created with external link functionality.Affected if Any external link pages exist in the system
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Inspect cvName parameter handling in updateCollectionAliasExternalLocate the updateCollectionAliasExternal function in the codebase (typically in collection handling or page type controller files). Examine the function for whether cvName parameter is sanitized before storage - check for proper encoding/escaping functions.Affected if The function lacks input sanitization or output encoding on the cvName parameter
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Review stored cvName values in databaseQuery the Pages or Collections table (often concrete_pages or Collections table) for records where cType is 'external' or similar. Inspect the cvName or page name field for any suspicious script tags or HTML attributes.Affected if Any external link page entries contain unescaped HTML/script content in the cvName field
A user is affected if running Concrete CMS version 9.5.0 or lower AND external link pages exist with unsanitized cvName values containing script tags.
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.
From vendor dataUpgrade Concrete CMS to a version newer than 9.5.0, or apply the vendor patch to ensure updateCollectionAliasExternal properly sanitizes the cvName parameter before storage.
- Consultation2.0 h
- Implementation4.0 h
- Testing6.0 h
- Review / QA3.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2026-8139 — 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-2026-8139 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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- Version or environment caveats, and links to real fixes
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