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Joomla\!Application · Joomla

CVE-2021-23129

MEDIUM · 6.1 CVSS v3.1 Published 2021-03-04
Fix available
A fix is available. Upgrade to 3.9.25 or later.
See remediation →
68/100
Remediation priority · Elevated
Remotely reachable No privileges

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! 2.5.0 through 3.9.24. Missing filtering of messages showed to users that could lead to xss issues.

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

A stored cross-site scripting (XSS) vulnerability in Joomla! versions 2.5.0 through 3.9.24 allows attackers to inject malicious scripts through unsanitized messages that are displayed to users. The missing input filtering on user-facing messages enables the execution of arbitrary JavaScript in victims' browsers.

MitigationUpgrade Joomla! to version 3.9.25 or later, which includes proper input validation and output encoding for displayed messages to prevent XSS exploitation.

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:>= 2.5.0, < 3.9.25

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
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 checks

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

  1. Identify Joomla! version
    Access the administrator dashboard and navigate to Help > System Information, or check the libraries/joomla/version.php file for the VERSION constant
    Affected if the installed version falls within 2.5.0 through 3.9.24 (versions greater than or equal to 2.5.0 and less than 3.9.25)
  2. Confirm message display functionality is in use
    Review the site configuration and templates to determine if components that display user-submitted messages (such as contact forms, user profiles, or messaging modules) are enabled and publicly accessible
    Affected if any feature that displays user-generated messages to visitors is active on the site

Your environment is affected if Joomla! version is 3.9.24 or earlier and user-submitted messages are displayed to users without additional sanitization layers.

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.

From vendor data
Upgrade available Upgrade to 3.9.25 or later
Fixed in 3.9.25
Interim mitigation

Upgrade Joomla! to version 3.9.25 or later, which includes proper input validation and output encoding for displayed messages to prevent XSS exploitation.

Fix this in Joomla\! Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA1.0 h
10.0 hours of engineering $1,750
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,800.

Scan for this in your stack

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dbcve dependency scanner

Check whether your project pulls in CVE-2021-23129 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

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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-2021-23129 in production — separate from our analysis above.

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.

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