CVE-2021-37151
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 · uneditedCyberArk Identity 21.5.131, when handling an invalid authentication attempt, sometimes reveals whether the username is valid. In certain authentication policy configurations with MFA, the API response length can be used to differentiate between a valid user and an invalid one (aka Username Enumeration). Response differentiation enables attackers to enumerate usernames of valid application users. Attackers can use this information to leverage brute-force and dictionary attacks in order to discover valid account information such as passwords.
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 confidenceCyberArk Identity 21.5.131 contains a username enumeration vulnerability where API responses differ in length depending on whether a username is valid, specifically when MFA authentication policies are configured. Attackers can distinguish valid from invalid usernames by comparing response sizes, enabling subsequent brute-force attacks.
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< 21.11.133CVSS 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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Identify CyberArk Identity installationLocate CyberArk Identity components on the server. Common installation paths include C:\Program Files\CyberArk\ or /opt/cyberark/. Check for identity provider service processes.Affected if CyberArk Identity is installed on the system
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Determine installed versionCheck the version of CyberArk Identity by examining the installed application files, registry entries (HKLM\Software\CyberArk\Identity), or the administration console. Compare the version number to the affected range: versions before 21.11.133 are vulnerable.Affected if Installed version is lower than 21.11.133
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Verify MFA authentication policies are configuredAccess the CyberArk Identity administration portal and navigate to Authentication > Policies or Security > MFA Policies. Review whether Multi-Factor Authentication policies have been defined and are active.Affected if MFA authentication policies are configured and active
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Test API response consistencySend authentication requests with both valid and invalid usernames to the API endpoint (typically /api/...). Compare the HTTP response Content-Length headers and response body sizes between requests with valid vs invalid usernames when MFA policies are in effect.Affected if Response sizes differ between valid and invalid usernames
A defender is affected if CyberArk Identity version is below 21.11.133 AND MFA authentication policies are configured, as the combination enables username enumeration via response size differences.
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 · scoped21.11.133
Normalize API response lengths and timings for authentication failures regardless of username validity, regardless of MFA policy configuration.
21.11.133 or later
- Identify all CyberArk Identity instances running versions prior to 21.11.133
- Review CyberArk release notes for version 21.11.133 to understand the security fixes included
- Schedule a maintenance window for the upgrade
- Back up the current CyberArk Identity configuration and database
- Upgrade CyberArk Identity to version 21.11.133 or later following the official upgrade documentation
- After upgrade, verify the vulnerability is fixed by testing authentication responses with both valid and invalid usernames to confirm response lengths are now consistent
- Monitor authentication logs to confirm the username enumeration issue is resolved
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation4.0 h
- Implementation8.0 h
- Testing4.0 h
- Review / QA2.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2021-37151 — 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-2021-37151 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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