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Fencer Vulns
medium 5.3

CVE-2025-13591 json

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

published 2026-10-19 20 d ago modified 2026-11-04 4 d ago also EUVD-2025-211119

cvss
5.3
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 22%
public exploits
0
none known

Summary

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.

Patch / fix

  • WSO2 WSO2 Identity Server 7.0.0.134, 7.1.0.42
  • WSO2 WSO2 Carbon Abstract OTP Authenticator 1.0.5.3, 1.0.10.2
  • WSO2 Email OTP Authenticator 1.0.18.8, 1.0.30.5

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
19 d ago

Exploit prediction

0.30% chance of exploitation in the next 30 days, higher than 22% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

Affected products

  • WSO2 WSO2 Identity Server
  • WSO2 WSO2 Carbon Abstract OTP Authenticator
  • WSO2 Email OTP Authenticator

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.