dbcve.org
Joomla\!Application · Joomla

CVE-2021-23128

CRITICAL · 9.1 CVSS v3.1 Published 2021-03-04
Fix available
A fix is available. Upgrade to 3.9.25 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 issue was discovered in Joomla! 3.2.0 through 3.9.24. The core shipped but unused randval implementation within FOF (FOFEncryptRandval) used an potential insecure implemetation. That has now been replaced with a call to 'random_bytes()' and its backport that is shipped within random_compat.

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! versions 3.2.0 through 3.9.24 shipped with a vulnerable random number generator in the FOF (Framework on Framework) library's FOFEncryptRandval class. This insecure implementation could allow attackers to predict or brute-force cryptographic values used for sessions, tokens, or other security-sensitive operations.

MitigationUpgrade Joomla! to version 3.9.25 or later, which replaces the insecure random number generation in FOFEncryptRandval with cryptographically secure random_bytes() and its random_compat backport.

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:>= 3.2.0, < 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
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

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

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

  1. Check Joomla version
    Locate the version.php file in your Joomla installation (typically in /libraries/cms/version.php or access it via the Joomla administrator dashboard under Help > System Info > PHP Information). Identify the RELEASE and DEV_LEVEL values.
    Affected if The installed version is 3.2.0 through 3.9.24 (RELEASE 3.x with DEV_LEVEL 0-24)
  2. Identify FOF library presence
    Look for the FOF (Framework on Framework) library in your installation, typically under /libraries/fof or /libraries/fof30. Check for the existence of the FOFEncryptRandval class file.
    Affected if The FOF library directory exists and contains FOFEncryptRandval.php
  3. Inspect FOFEncryptRandval implementation
    Open the FOFEncryptRandval.php file in the fof/encrypt directory. Examine the class for use of mt_rand(), mt_srand(), or other non-cryptographically secure random functions.
    Affected if The class uses mt_rand(), mt_srand(), or similar weak random number generation functions instead of random_bytes() or random_int()
  4. Check for token/session usage
    Search configuration files and session handlers for references to FOFEncryptRandval or the FOF encryption library being used for token generation, session IDs, or security tokens.
    Affected if FOFEncryptRandval is actively referenced in code that generates sessions, tokens, or other security-sensitive values

Your environment is affected if Joomla version is 3.2.0 through 3.9.24 AND the FOFEncryptRandval class with insecure random generation is present and in use.

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 3.9.25 or later
Fixed in 3.9.25
Interim mitigation

Upgrade Joomla! to version 3.9.25 or later, which replaces the insecure random number generation in FOFEncryptRandval with cryptographically secure random_bytes() and its random_compat backport.

Recommended fix High confidence

3.9.25

  1. Upgrade Joomla! to version 3.9.25 or later

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

Fix this in Joomla\! Scoped from the published advisory
  • Consultation1.0 h
  • Implementation1.0 h
  • Testing1.0 h
  • Review / QA1.0 h
4.0 hours of engineering $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 $1,200.

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-2021-23128 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