Joomla\!Application · Joomla
CVE-2021-26032
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 3.9.26. HTML was missing in the executable block list of MediaHelper::canUpload, leading to XSS attack vectors.
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 confidenceA cross-site scripting (XSS) vulnerability exists in Joomla! versions 3.0.0 through 3.9.26. The MediaHelper::canUpload function maintains a block list of executable file types to prevent malicious uploads, but HTML files were not included in this block list. Attackers could upload HTML files containing malicious scripts that would execute when users view the uploaded files, leading to XSS attacks.
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, <= 3.9.26CVSS 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
- Required
- Scope
- Changed
- Confidentiality
- Low
- Integrity
- Low
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/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.
-
Determine Joomla versionLog into the Joomla Administrator dashboard and navigate to System > System Information > Joomla! Version, or check the /libraries/cms/version.php file for the VERSION constant.Affected if The installed version is between 3.0.0 and 3.9.26 inclusive.
-
Confirm Media component is accessibleNavigate to Content > Media Manager in the Joomla Administrator panel and verify the component loads successfully.Affected if The Media component is enabled and accessible to users who can upload files.
-
Check if HTML is in the executable file block listExamine the MediaHelper::canUpload function in /libraries/src/MediaHelper.php (or the equivalent file in your installation) and inspect the $_executable array or block list definition to determine if 'html' or 'htm' extensions are listed as blocked executable types.Affected if HTML and HTM extensions are NOT present in the blocked executable file types list.
-
Verify upload functionality is enabledIn the Media Manager, attempt to access the upload feature or check the global configuration under Content > Media Manager for upload permissions.Affected if File upload functionality is permitted for the user role in question.
You are affected if your Joomla version is between 3.0.0 and 3.9.26, the Media component is enabled, and HTML files are not included in the executable file type block list.
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 Joomla! to version 3.9.27 or later, which includes HTML in the executable block list. As a temporary workaround, disable or restrict file uploads in the Media component until the patch can be applied.
Fix this in Joomla\!
Scoped from the published advisory
- Consultation2.0 h
- Implementation1.0 h
- Testing4.0 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 $2,464.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-26032 — 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-2021-26032 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
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.
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