Joomla\!Application · Joomla
CVE-2021-26027
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 · uneditedAn issue was discovered in Joomla! 3.0.0 through 3.9.24. Incorrect ACL checks could allow unauthorized change of the category for an article.
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 · moderate confidenceJoomla! CMS versions 3.0.0 through 3.9.24 contain an incorrect Access Control List (ACL) check vulnerability in the core application. This flaw allows authenticated users with limited privileges to bypass authorization controls and modify the category assignment of articles they should not have access to modify.
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
Joomla\!Application
>= 3.0.0, < 3.9.25CVSS 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 checksWork through these to decide whether this CVE applies to you.
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Identify Joomla CMS installationLocate the Joomla installation directory and check for the presence of configuration.php or administrator/manifest.php files that confirm Joomla CMS.Affected if The system is running Joomla CMS and the installation directory is found.
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Determine installed Joomla versionOpen the file /libraries/cms/version/version.php (or check the manifest file at /administrator/manifests/files/joomla.xml) and locate the 'RELEASE' and 'DEV_LEVEL' constants to determine the exact version number.Affected if The installed version is 3.9.24 or earlier (version falls within 3.0.0 through 3.9.24).
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Verify version is in vulnerable rangeCompare the detected version against the affected range: 3.0.0 <= version < 3.9.25. If the version is 3.9.24 or earlier, the installation is vulnerable.Affected if The installed version is 3.9.24 or any version from 3.0.0 through 3.9.24.
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Confirm user registration is enabledCheck in the Joomla administrator panel under Users > Manage or in configuration.php whether self-registration or user account creation is permitted, or inspect the #__users table in the database.Affected if The site allows user registration or has existing registered users beyond the administrator account.
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Verify article and category features are activeCheck that the core com_content component is enabled and that articles and categories exist in the database (tables #__content and #__categories). The vulnerability exploits category assignment in articles.Affected if The Joomla content component is active and contains articles and categories that could be reassigned by a limited-privilege user.
If the installed Joomla version is 3.9.24 or earlier (3.0.0 through 3.9.24) and the site has authenticated users with limited privileges who can access articles, the environment is affected by this ACL bypass vulnerability.
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 data3.9.25
Update Joomla! CMS to version 3.9.25 or later, which contains the patched ACL validation logic. Verify user permissions and review access logs for any unauthorized category changes that may have occurred prior to patching.
Fix this in Joomla\!
Scoped from the published advisory
- Consultation2.0 h
- Implementation3.0 h
- Testing4.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,752.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-26027 — 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-2021-26027 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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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.
- 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