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Joomla\!Application · Joomla

CVE-2026-40383

CRITICAL · 9.8 CVSS v3.1 Published 2026-05-26
Fix available
A fix is available. Upgrade to 5.4.6 / 6.1.1 or later.
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 improper validation of user-supplied input leads to a local file inclusion vulnerability.

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 confidence

A local file inclusion (LFI) vulnerability exists due to improper validation of user-supplied input. Attackers can manipulate file inclusion parameters to read arbitrary files on the server, potentially exposing sensitive configuration files, credentials, and source code.

MitigationImplement strict whitelist-based input validation for file inclusion parameters and use direct file reading methods instead of dynamic inclusion where possible to prevent path traversal 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
Affected:>= 3.2.1, < 5.4.6>= 6.0.0, < 6.1.1

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
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/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. Identify installed Joomla version
    Access the administrator backend and navigate to System > System Information or check the libraries/cms.php file for the VERSION constant. Alternatively, check the administrator/manifests/files/joomla.xml file.
    Affected if The installed version falls within >= 3.2.1, < 5.4.6 or >= 6.0.0, < 6.1.1
  2. Verify file inclusion functionality is accessible
    Check if any third-party or core components that handle file paths or template includes are installed and publicly accessible. Review installed components in Components > Manage.
    Affected if Any component using dynamic file inclusion based on user input is enabled and exposed to unauthenticated users
  3. Review configuration for file path settings
    Examine the configuration.php file for any allow_url_fopen or custom file path settings, and check System > Global Configuration for any file inclusion-related parameters.
    Affected if Configuration permits dynamic file path construction from request parameters

The environment is affected if the Joomla version is 3.2.1 through 5.4.5, or 6.0.0 through 6.1.0, and file inclusion functionality based on user input is accessible.

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
Upgrade available Upgrade to 5.4.6 / 6.1.1 or later
Fixed in 5.4.66.1.1
Interim mitigation

Implement strict whitelist-based input validation for file inclusion parameters and use direct file reading methods instead of dynamic inclusion where possible to prevent path traversal attacks.

Recommended fix High confidence

Joomla 5.4.6 or later (5.x branch); Joomla 6.1.1 or later (6.x branch)

  1. 1. Create a complete backup of your Joomla database and all website files
  2. 2. Review the Joomla 5.4.6 (for 5.x branch) or 6.1.1 (for 6.x branch) release notes for any specific upgrade requirements
  3. 3. Verify your PHP version meets the minimum requirements for the target Joomla version
  4. 4. Use the Joomla Update component in the admin dashboard to install the update, or manually upload the new version via FTP
  5. 5. After upgrading, clear any cached files
  6. 6. Test critical site functionality including content, extensions, and templates to ensure compatibility
  7. 7. Verify the path traversal vulnerability is resolved by confirming user input is properly validated
Caveat Review extension and template compatibility before upgrading; major version jumps may require updates to third-party extensions

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
  • Testing4.0 h
  • Review / QA2.0 h
18.0 hours of engineering $3,200
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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-2026-40383 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