Joomla\!Application · Joomla
CVE-2021-26038
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! 2.5.0 through 3.9.27. Install action in com_installer lack the required hardcoded ACL checks for superusers. A default system is not affected cause the default ACL for com_installer is limited to super users already.
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 confidenceJoomla! versions 2.5.0 through 3.9.27 contain a missing hardcoded ACL check in the com_installer component's Install action. While default Joomla installations restrict com_installer to superusers via default ACL rules, systems that have modified their ACL configuration to be more permissive lack proper enforcement at the code level, potentially allowing unauthorized users to access installation functionality.
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
>= 2.5.0, <= 3.9.27CVSS 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
- High
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/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 Joomla versionNavigate to Help > System Information > Joomla! Version in the admin panel, or check the version.php file in the /libraries/cms/version/ directoryAffected if Installed version is between 2.5.0 and 3.9.27 inclusive
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Verify com_installer ACL configurationIn the admin panel, go to Components > com_installer > Options, or inspect the #__assets table in the database for the com_installer asset entry. Check the rules column to see which user groups have accessAffected if The com_installer component allows access from user groups other than Super Users
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Identify non-superuser accountsReview the #__users and #__user_usergroup_map tables in the database to enumerate user accounts and their assigned groupsAffected if Non-superuser accounts exist in the system
You are affected only if your Joomla version is within 2.5.0-3.9.27 AND the com_installer component ACL has been relaxed to permit non-superuser access, allowing unauthorized users to reach installation functionality
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 dataEnsure the com_installer component ACL remains restricted to superuser accounts; if previously modified, revert to superuser-only access. Apply vendor patches when available.
Fix this in Joomla\!
Scoped from the published advisory
- Consultation2.0 h
- Implementation4.0 h
- Testing3.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,088.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-26038 — 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-2021-26038 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
- No spam, self-promotion, credentials, or personal data