CVE-2025-13591

Username Enumeration via Authentication Endpoint in WSO2 Identity Server Allows User Account Discovery

Published Oct 19, 2026 CVSS 3.1 · 5.3 Medium EPSS < 1% KEV · Not listed
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.

Remediation

Vendor Solution

Follow the instructions given on https://security.docs.wso2.com/en/latest/security-announcements/security-advisories/2026/WSO2-2025-4583/#solution

Tracking

Sign in to view the affected projects.

Advisories

No advisories available
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared Wso2 identity Server
Vendors & Products Wso2 identity Server
Type Values Removed Values Added
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.
Title Username Enumeration via Authentication Endpoint in WSO2 Identity Server Allows User Account Discovery
First Time appeared Wso2
Wso2 email Otp Authenticator
Wso2 wso2 Carbon Abstract Otp Authenticator
Wso2 wso2 Identity Server
Weaknesses CWE-203
CPEs cpe:2.3:a:wso2:email_otp_authenticator:*:*:*:*:*:*:*:*
cpe:2.3:a:wso2:wso2_carbon_abstract_otp_authenticator:*:*:*:*:*:*:*:*
cpe:2.3:a:wso2:wso2_identity_server:*:*:*:*:*:*:*:*
Vendors & Products Wso2
Wso2 email Otp Authenticator
Wso2 wso2 Carbon Abstract Otp Authenticator
Wso2 wso2 Identity Server
References
Metrics cvssV3_1

{'score': 5.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
WSO2
Published
Updated
Oct 20, 2026, 7:32 PM
Reserved
Nov 24, 2025, 5:16 AM
Status
Awaiting Analysis
Published
Oct 19, 2026, 5:16 PM
Modified
Nov 4, 2026, 8:10 PM