CVE-2025-13591 Username Enumeration via Authentication Endpoint in WSO2 Identity Server Allows User Account Discovery
Attackers can enumerate valid usernames via inconsistent authentication responses, facilitating targeted attacks like phishing or brute force.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2025-13591?
CVE-2025-13591 is a medium-severity vulnerability in WSO2 Email OTP Authenticator, published on 19 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-203
Which versions are affected by CVE-2025-13591?
How do I fix CVE-2025-13591?
No fix has been published for CVE-2025-13591 yet. Limit exposure of the affected software until one is available.
Is CVE-2025-13591 being exploited?
There is no known exploitation of CVE-2025-13591 in the wild and no public exploit code.
Sources
Also known as GHSA-9j2j-6wwh-jwf6.