# CVE-2021-3754: Keycloak's improper input validation allows using email as username

> Attackers can register with usernames matching existing user emails, potentially disrupting password recovery processes for legitimate users.

- **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 26 Aug 2022
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-4vc8-pg5c-vg4x

## What is CVE-2021-3754?

CVE-2021-3754 is a medium-severity vulnerability in Redhat Keycloak, published on 26 Aug 2022. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A flaw was found in keycloak where an attacker is able to register himself with the username same as the email ID of any existing user. This may cause trouble in getting password recovery email in case the user forgets the password.

Weakness: CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2021-3754?

2 open source packages ship an affected version, including org.keycloak:keycloak-services. It affects 2 products.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `org.keycloak:keycloak-services` | Maven | All versions | 24.0.1 |
| `org.keycloak:keycloak-services` | Maven | All versions | 24.0.1 |

Products: Redhat Keycloak, Redhat Single Sign-On.

## How do I fix CVE-2021-3754?

Upgrade org.keycloak:keycloak-services to 24.0.1 or later.

## Is CVE-2021-3754 being exploited?

There is no known exploitation of CVE-2021-3754 in the wild and no public exploit code.

Public exploit code:

- Vulnerability details and exploit for CVE-2021-3754 (github_poc): https://github.com/7Ragnarok7/CVE-2021-3754

## Other vulnerabilities in Redhat Keycloak

- [CVE-2022-4361](https://insights.sbomify.com/CVE-2022-4361/): Keycloak vulnerable to cross-site scripting when validating URI-schemes on SAML and OIDC (critical 10.0)
- [CVE-2022-1245](https://insights.sbomify.com/CVE-2022-1245/): Keycloak vulnerable to privilege escalation on Token Exchange feature (critical 9.8)
- [CVE-2021-20195](https://insights.sbomify.com/CVE-2021-20195/): keycloak Self Stored Cross-site Scripting vulnerability (critical 9.6)
- [CVE-2019-14910](https://insights.sbomify.com/CVE-2019-14910/): Keycloak Authentication Error (critical 9.3)
- [CVE-2019-14909](https://insights.sbomify.com/CVE-2019-14909/): Keycloak Authentication Error (critical 9.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-3754 and fix it if it is affected.

What it is: CVE-2021-3754 is a medium-severity vulnerability in Redhat Keycloak, published on 26 Aug 2022. 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-2021-3754 in the wild and no public exploit code.

Affected packages and fixed versions:
- org.keycloak:keycloak-services (Maven): affected all versions; fixed in 24.0.1
- org.keycloak:keycloak-services (Maven): affected all versions; fixed in 24.0.1

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-2021-3754/ (Markdown: https://insights.sbomify.com/CVE-2021-3754/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-3754
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-3754
- OSV: https://osv.dev/vulnerability/CVE-2021-3754

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-3754/
Summaries are generated and may contain mistakes; the official description above is the record.