Joomla\!Application · Joomla
CVE-2021-23127
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 an insufficient length for the 2FA secret accoring to RFC 4226 of 10 bytes vs 20 bytes.
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 confidenceJoomla versions 3.2.0 through 3.9.24 use an insufficient 10-byte secret for TOTP-based two-factor authentication instead of the RFC 4226 compliant 20-byte secret. This reduces the entropy of generated 2FA codes, weakening the authentication mechanism and potentially making brute-force attacks more feasible.
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
- 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 checksWork through these to decide whether this CVE applies to you.
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Check your Joomla versionNavigate to Joomla admin dashboard > Help > About or check the libraries/cms.php file for the version constantAffected if The version is 3.2.0 through 3.9.24 (anything >= 3.2.0 and < 3.9.25)
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Identify if TOTP 2FA is configuredCheck the Joomla user manager for users with two-factor authentication enabled, or query the database for users with non-empty 2FA secret fieldsAffected if Any user accounts have TOTP-based two-factor authentication enabled on this Joomla installation
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Inspect the stored TOTP secret lengthExamine the secret value stored in the database for users with 2FA enabled. TOTP secrets are Base32-encoded; a 10-byte secret encodes to 16 Base32 characters, while a proper 20-byte secret encodes to 32 Base32 charactersAffected if The stored secret is 16 Base32 characters (10 bytes) instead of 32 characters (20 bytes), indicating the weak secret format is in use
You are affected if your Joomla version is between 3.2.0 and 3.9.24 and you have users with TOTP 2FA enabled using the weaker 10-byte secret format.
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.
dbcve · scoped3.9.25
Upgrade Joomla to version 3.9.25 or later which implements the proper 20-byte secret length per RFC 4226. Existing 2FA secrets should be re-generated after the update.
Joomla! 3.9.25
- Create a complete backup of the Joomla site files and database before proceeding
- Download Joomla! 3.9.25 from the official Joomla! downloads page (downloads.joomla.org)
- Log in to the Joomla Administrator backend
- Navigate to Components > Joomla Update
- Either use the one-click update feature if it detects the new version, or upload the downloaded Joomla 3.9.25 package
- Follow the on-screen installation prompts to complete the upgrade
- Run any pending database migrations when prompted
- Clear the Joomla cache (System > Clear Cache)
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Joomla\!
Scoped from the published advisory
- Consultation2.0 h
- Implementation4.0 h
- Testing3.0 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 $3,088.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-23127 — 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-2021-23127 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
- No spam, self-promotion, credentials, or personal data