CVE-2021-21020
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 · uneditedMagento versions 2.4.1 (and earlier), 2.4.0-p1 (and earlier) and 2.3.6 (and earlier) are vulnerable to an access control bypass vulnerability in the Login as Customer module. Successful exploitation could lead to unauthorized access to restricted resources.
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 confidenceMagento versions 2.4.1 and earlier, 2.4.0-p1 and earlier, and 2.3.6 and earlier contain an access control bypass vulnerability in the Login as Customer module. Successful exploitation allows unauthorized access to restricted resources.
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< 2.3.6= 2.3.6= 2.4.0= 2.4.1CVSS 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
- High
- Privileges
- None
- User interaction
- Required
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- High
- Availability
- None
CVSS:3.0/AV:N/AC:H/PR:N/UI:R/S:U/C:N/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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Determine installed Magento versionRun 'php bin/magento --version' from the Magento root directory, or check the 'version' field in composer.json, or view the version in the Admin panel under System > Tools > Web Setup Wizard > System UpgradeAffected if The version is 2.3.6, 2.4.0, 2.4.1, or any version earlier than these (2.4.0-p1 and earlier, or 2.4.1 and earlier)
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Locate Login as Customer moduleCheck if the module exists in vendor/magento/module-login-as-customer or run 'php bin/magento module:status | grep LoginAsCustomer'Affected if The module is present in the installation
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Verify module is enabledRun 'php bin/magento module:status Magento_LoginAsCustomer' or check app/etc/config.php for 'Magento_LoginAsCustomer' => 1Affected if The module shows as enabled or '1' in config.php
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Check module configuration settingsInspect the module's etc/acl.xml or etc/adminhtml/routes.xml files in vendor/magento/module-login-as-customer to verify access control definitions exist and are properly restrictedAffected if Access control definitions are missing, misconfigured, or allow unrestricted access to the module routes
You are affected if your Magento installation version is 2.3.6, 2.4.0, 2.4.1, or any earlier version AND the Login as Customer module is enabled and accessible without proper authorization controls.
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 data2.3.6
Apply the official Magento security patch or upgrade to a patched version (2.4.2, 2.4.1-p1, or 2.3.7) to remediate this access control vulnerability.
- Consultation2.0 h
- Implementation4.0 h
- Testing2.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,560.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-21020 — 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-2021-21020 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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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.
- 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