CVE Intelligence
Medium Info disclosure

CVE-2025-13591 — Username Enumeration via Authentication Endpoint in WSO2 Identity Server Allows User Account Discovery

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.

Published Oct 19, 2026 · Updated Oct 19, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: WSO2

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.
How the score was calculated
  • Technical severity (medium)+3

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation
Not confirmed
Not in CISA KEV — an absence of record, not proof it is unexploited.
EPSS FIRST
—
No EPSS score.
Affects
WSO2
Email OTP Authenticator and 2 more
CVSS base
5.3
Medium · 2 source(s)

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

  1. Identify exposed assets running the affected vendor/product/version combinations (WSO2 Email OTP Authenticator, WSO2 Identity Server, WSO2 WSO2 Carbon Abstract OTP Authenticator).
  2. The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
  3. No fix documented in the sources: reduce exposure and monitor the vendor advisory.
  4. Search available logs for exploit probes matching the vulnerability class (info disclosure), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

VendorProductVersionsStatusSource
WSO2 Email OTP Authenticator ≥ 1.0.18 and < 1.0.18.8≥ 1.0.30 and < 1.0.30.5 Vulnerable CVE Program (cve.org) e CISA ADP
WSO2 Identity Server ≥ 7.0.0 and < 7.0.0.134≥ 7.1.0 and < 7.1.0.42 Vulnerable CVE Program (cve.org) e CISA ADP
WSO2 WSO2 Carbon Abstract OTP Authenticator ≥ 1.0.5 and < 1.0.5.3≥ 1.0.10 and < 1.0.10.2 Vulnerable CVE Program (cve.org) e CISA ADP

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
None
Availability
None

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

ScoreVersionSeverityExpl.ImpactScored by
5.3 CVSS 3.1 Medium 3.9 1.4 ed10eef1-636d-4fbe-9993-6890dfa878f8 via NIST National Vulnerability Database
5.3 CVSS 3.1 Medium — — WSO2 via CVE Program (cve.org) e CISA ADP
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N (score shown at the top: ed10eef1-636d-4fbe-9993-6890dfa878f8)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-203 · Observable Discrepancy

Other CVEs with this weakness →

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

  • Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
  • Look for anomalous data read/export volumes and access to sensitive records.
web/proxy/WAF logsnetwork IDS/IPSapplication logsauthentication logs

Timeline

What happened to this CVE, newest first.

  • 2026
  • Source status changed · Received → Awaiting Analysis
    Oct 19, 2026 · NIST National Vulnerability Database
  • Affected products added · wso2/wso2 identity server, wso2/wso2 carbon abstract otp authenticator, wso2/email otp authenticator
    Oct 19, 2026 · CVE Program (cve.org) e CISA ADP
  • Record published
    Oct 19, 2026
  • CVSS changed · 5.3
    Oct 19, 2026 · NIST National Vulnerability Database
  • Source status changed · → Received
    Oct 19, 2026 · NIST National Vulnerability Database
  • Record created in this database
    Oct 19, 2026 · Alertas do Telegram
  • CVE published
    Oct 19, 2026 · WSO2

Source activity

Repeated readings are counted rather than listed.

  • 1× References added · Oct 19, 2026 – Oct 19, 2026
  • 1× Official description updated · Oct 19, 2026 – Oct 19, 2026

References

1 on the record

Elsewhere on this site

WSO2
every CVE for this vendor
Info disclosure
same class
CWE-203
other pages naming this weakness

Related CVEs (same products)

  • CVE-2025-7203 Sensitive Information Disclosure via Management Console and Product Files in Multiple WSO2 Products Allows Retrieval of Credentials 10h
  • CVE-2025-13173 Improper Token Revocation via Session-Bound Token Flow in Multiple WSO2 Products Allows Unauthorized Access After Session Termination 10h
  • CVE-2025-10149 Arbitrary Operations via SCIM Endpoints in Multiple WSO2 Products Enables User Account Takeover 10h
  • CVE-2024-4412 Expression Language Injection via User Input in Multiple WSO2 Products Permits Arbitrary Operations 10h
  • CVE-2024-4457 Remote Code Execution via JDBC User Store Configuration in Multiple WSO2 Products Allows Arbitrary Code Execution 1d
  • CVE-2024-8122 Potential brute force vulnerability due to non-expiring SMS OTPs 12d

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

  • No FIRST EPSS score.
  • No fixed version, patch or mitigation documented.
  • No CISA SSVC assessment.
  • No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
  • No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
  • No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2025-13591 is "Username Enumeration via Authentication Endpoint in WSO2 Identity Server Allows User Account Discovery", rated Medium. It affects Email OTP Authenticator (WSO2); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 5.3 describes technical severity. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

Comments

Moderated technical discussion. Read the community guidelines.

No comments yet.

Sign in or create an account to comment and suggest corrections.