dbcve.org
Joomla\!Application · Joomla

CVE-2021-26040

CRITICAL · 9.1 CVSS v3.1 Published 2021-08-24
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

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 · unedited
An issue was discovered in Joomla! 4.0.0. The media manager does not correctly check the user's permissions before executing a file deletion command.

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 confidence

Joomla! 4.0.0 contains a broken access control vulnerability in the media manager component. The application fails to properly verify user permissions before processing file deletion requests, allowing authenticated attackers (or potentially unauthenticated depending on the specific attack vector) to delete arbitrary files on the server by manipulating the media manager deletion function.

MitigationUpgrade to Joomla 4.0.1 or later which contains the proper permission check fix. As an immediate workaround, restrict administrative access to trusted users only until the patch can be applied.

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
Affected:= 4.0.0

CVSS 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
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H

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 checks

Work through these to decide whether this CVE applies to you.

  1. Check Joomla installation version
    Locate the version.php file in the Joomla installation directory (typically in /libraries/src/Version.php or check the administrator/manifests/files/joomla.xml file) and read the version number defined there.
    Affected if The installed version is exactly 4.0.0 (no patches applied)
  2. Verify media manager component is accessible
    Log into the Joomla administrator panel and navigate to Content > Media (or access /administrator/index.php?option=com_media) to confirm the media manager component is present and functional.
    Affected if The media manager component is accessible and functional in the Joomla installation
  3. Confirm user access to media manager deletion function
    In the Joomla admin panel, go to Users > Access Levels and examine which user groups have permission to access and use the media manager component (component permission for com_media). Check if any user group beyond administrators has delete permissions.
    Affected if Non-administrator users or user groups have access to the media manager with deletion capabilities
  4. Inspect media model deletion code (if code accessible)
    If you have access to the Joomla source code, examine the file /administrator/components/com_media/src/Model/ApiModel.php (or similar media model files) around the delete function to verify if the permission check (typically $this->app->getIdentity()->authorise('core.delete', 'com_media')) is properly implemented before file deletion.
    Affected if The code lacks or has a flawed permission check before the delete operation in the media model

You are affected if Joomla 4.0.0 is installed and the media manager component is accessible to users without proper permission validation on file deletion operations.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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 · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade to Joomla 4.0.1 or later which contains the proper permission check fix. As an immediate workaround, restrict administrative access to trusted users only until the patch can be applied.

Recommended fix High confidence

Joomla! 4.x latest stable release (newer than 4.0.0)

  1. 1. Back up your Joomla! 4.0.0 installation including database and files
  2. 2. Download the latest stable Joomla! 4.x release from the official Joomla! download page
  3. 3. Extract the upgrade package to a temporary location
  4. 4. Use Joomla's built-in Joomla! Update component to install the update, or manually replace core files
  5. 5. Clear all Joomla caches after the upgrade
  6. 6. Verify that the media manager file deletion now properly enforces authorization checks
  7. 7. Test that users without proper permissions cannot delete files via the media manager
Caveat Standard Joomla minor version upgrade - review release notes for any configuration or extension compatibility changes

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Joomla\! Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing8.0 h
  • Review / QA4.0 h
24.0 hours of engineering $4,160
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Scan for this in your stack

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-26040 in production — separate from our analysis above.

No notes yet

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What this is

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.

What belongs here
  • 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