CVE-2025-13591: wso2 email otp authenticator Observable Discrepancy

Vulnerability summary

CVE-2025-13591 is a medium (CVSS 5.3) Observable Discrepancy vulnerability in wso2 email otp authenticator. EPSS estimates a 0.22% chance of exploitation in the next 30 days, higher than 12.3% of scored vulnerabilities.

Timeline

1. 19-10-2026
   PublishedVulnerability first disclosed.

Description

The authentication endpoint of WSO2 Identity Server fails to provide a consistent system response when a username does not exist in the system, allowing attackers to differentiate between valid and invalid usernames. This difference in responses can be leveraged to enumerate existing user accounts. Successful exploitation enables an attacker to discover valid usernames within the system, significantly increasing the risk of subsequent attacks such as brute force attacks on user credentials, social engineering attacks, and information leakage. The discovered usernames can be used to craft targeted phishing emails or other social engineering campaigns.

• CWE-203Observable DiscrepancyThe product behaves differently or sends different responses under different circumstances in a way that is observable to an unauthorized actor.