Joomla\!Application · Joomla
CVE-2021-23126
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! 3.2.0 through 3.9.24. Usage of the insecure rand() function within the process of generating the 2FA secret.
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 confidenceThe vulnerability involves the use of the cryptographically insecure rand() function during Two-Factor Authentication (2FA) secret generation in Joomla! CMS versions 3.2.0 through 3.9.24. This could potentially allow an attacker to predict or guess 2FA secrets due to the predictable nature of rand(), undermining the security of the 2FA mechanism.
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
>= 3.2.0, < 3.9.25CVSS 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
- Low
- Integrity
- None
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/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.
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Check Joomla CMS versionLocate the file 'administrator/manifests/files_joomla.xml' or check the admin dashboard footer which displays the version number. Compare the installed version against the affected range: 3.2.0 through 3.9.24.Affected if The installed version is 3.2.0 or higher but lower than 3.9.25.
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Verify 2FA plugin is installedCheck for the presence of the twofactorauth plugins by examining the 'plugins/twofactorauth' directory in the Joomla installation. Look for subdirectories named 'totp' and/or 'yubikey'.Affected if Two-factor authentication plugins exist in the system.
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Confirm 2FA is enabledLog into the Joomla administrator panel and navigate to Plugins. Filter by 'twofactorauth' and check if either TOTP or YubiKey 2FA plugins are enabled (status = 'Enabled'). Alternatively, query the '#__extensions' database table for enabled twofactorauth plugins.Affected if At least one two-factor authentication plugin is enabled.
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Check if any users have 2FA configuredQuery the '#__user_keys' database table, which stores 2FA secrets for users. If any rows exist, users have configured 2FA on their accounts.Affected if Any rows exist in the user_keys table, indicating active 2FA secrets that were generated using the vulnerable rand() function.
The environment is affected if Joomla version is 3.2.0 through 3.9.24 AND two-factor authentication is enabled or any users have configured 2FA, because the insecure rand() function was used to generate their 2FA secrets.
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 data3.9.25
Upgrade Joomla! CMS to version 3.9.25 or later, which replaces the insecure rand() function with a cryptographically secure random number generator for 2FA secret generation.
Fix this in Joomla\!
Scoped from the published advisory
- Consultation2.0 h
- Implementation4.0 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 $3,328.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-23126 — 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-2021-23126 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
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- 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
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