# CVE-2025-13166: Username Enumeration via SMS OTP Flow in WSO2 Identity Server Allows User Account Discovery

> Attackers can enumerate valid usernames via SMS OTP error messages, facilitating brute force attacks and social engineering.

- **Severity:** Low 3.7 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 15 Sep 2026
- **Updated:** 15 Sep 2026
- **Also known as:** GHSA-xwj5-m236-f9hp

## What is CVE-2025-13166?

CVE-2025-13166 is a low-severity vulnerability in WSO2 Identity Server, published on 15 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

The SMS OTP flow fails to adequately handle error messages, allowing an attacker to infer the existence of registered user accounts based on the responses received during the OTP initiation process.

This weakness can be exploited by an attacker to discover valid usernames within the system. The impact is amplified for accounts that have not configured a mobile number, as the enumeration is specifically tied to this condition. The discovery of these usernames can facilitate subsequent brute force attacks, social engineering attempts, and information leakage, potentially leading to reputational damage, loss of customer trust, and regulatory non-compliance.

Weakness: CWE-203 (Observable Discrepancy)

## Which versions are affected by CVE-2025-13166?


## How do I fix CVE-2025-13166?

No fix has been published for CVE-2025-13166 yet. Limit exposure of the affected software until one is available.

## Is CVE-2025-13166 being exploited?

There is no known exploitation of CVE-2025-13166 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-13166 and fix it if it is affected.

What it is: CVE-2025-13166 is a low-severity vulnerability in WSO2 Identity Server, published on 15 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2025-13166 in the wild and no public exploit code.

Affected product: WSO2 Identity Server. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2025-13166/ (Markdown: https://insights.sbomify.com/CVE-2025-13166/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-13166
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-13166
- OSV: https://osv.dev/vulnerability/CVE-2025-13166

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-13166/
Summaries are generated and may contain mistakes; the official description above is the record.