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.

CyberArk - CWE-200: Exposure of Sensitive Information to an Unauthorized Actor

CyberArk - CWE-200: Exposure of Sensitive Information to an Unauthorized Actor

CyberArk - CWE-602: Client-Side Enforcement of Server-Side Security

CyberArk - CWE-200: Exposure of Sensitive Information to an Unauthorized Actor

CyberArk Identity versions up to and including 22.1 in the 'StartAuthentication' resource, exposes the response header 'X-CFY-TX-TM'. In certain configurations, that response header contains different, predictable value ranges which can be used to determine whether a user exists in the tenant.