# CVE-2018-25350: userSpice 4.3.24 Username Enumeration via existingUsernameCheck.php

> Unauthenticated attackers can enumerate valid usernames in userSpice by analyzing responses from the existingUsernameCheck.php endpoint.

- **Severity:** Critical 9.3 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 23 May 2026
- **Updated:** 26 May 2026
- **Also known as:** GHSA-56j3-w2r5-qgxq

## What is CVE-2018-25350?

CVE-2018-25350 is a critical vulnerability in userSpice, published on 23 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

userSpice 4.3.24 contains a username enumeration vulnerability that allows unauthenticated attackers to discover valid usernames by sending POST requests to the existingUsernameCheck.php endpoint. Attackers can submit usernames and analyze response text for the 'taken' string to identify existing accounts in the system.

Weakness: CWE-204 (Observable Response Discrepancy)

## Which versions are affected by CVE-2018-25350?


## How do I fix CVE-2018-25350?

No fix has been published for CVE-2018-25350 yet. Limit exposure of the affected software until one is available.

## Is CVE-2018-25350 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2018-25350 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2018-25350 and fix it if it is affected.

What it is: CVE-2018-25350 is a critical vulnerability in userSpice, published on 23 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2018-25350 exists.

Affected product: userSpice. 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-2018-25350/ (Markdown: https://insights.sbomify.com/CVE-2018-25350/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2018-25350
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2018-25350
- OSV: https://osv.dev/vulnerability/CVE-2018-25350

---
From sbomify Insights: https://insights.sbomify.com/CVE-2018-25350/
Summaries are generated and may contain mistakes; the official description above is the record.