# CVE-2021-3424: Keycloak is vulnerable to IDN homograph attack

> Attackers can use IDN homograph attacks to impersonate users and trick admins into granting extra privileges in Keycloak.

- **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 1 Jun 2021
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-pf38-cw3p-22q9

## What is CVE-2021-3424?

CVE-2021-3424 is a medium-severity authentication bypass vulnerability in Redhat Single Sign-On, published on 1 Jun 2021. 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 as shipped in Red Hat Single Sign-On 7.4 where IDN homograph attacks are possible. A malicious user can register himself with a name already registered and trick admin to grant him extra privileges.

Weakness: CWE-287 (Improper Authentication)

## Which versions are affected by CVE-2021-3424?

2 open source packages ship an affected version, including org.keycloak:keycloak-services. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `org.keycloak:keycloak-services` | Maven | All versions | 18.0.0 |
| `org.keycloak:keycloak-services` | Maven | All versions | 18.0.0 |

Products: Redhat Single Sign-On.

## How do I fix CVE-2021-3424?

Upgrade org.keycloak:keycloak-services to 18.0.0 or later.

## Is CVE-2021-3424 being exploited?

There is no known exploitation of CVE-2021-3424 in the wild and no public exploit code.

## Other vulnerabilities in Redhat Single Sign-On

- [CVE-2020-10695](https://insights.sbomify.com/CVE-2020-10695/): Privilege escalation in containers/redhat-sso-7 (high 7.8)
- [CVE-2022-2256](https://insights.sbomify.com/CVE-2022-2256/): Keycloak vulnerable to Stored Cross site Scripting (XSS) when loading default roles (low 3.8)
- [CVE-2020-14341](https://insights.sbomify.com/CVE-2020-14341/): Server-side request forgery in Red Hat Single Sign-On (low 2.7)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-3424 and fix it if it is affected.

What it is: CVE-2021-3424 is a medium-severity authentication bypass vulnerability in Redhat Single Sign-On, published on 1 Jun 2021. 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-2021-3424 in the wild and no public exploit code.

Affected packages and fixed versions:
- org.keycloak:keycloak-services (Maven): affected all versions; fixed in 18.0.0
- org.keycloak:keycloak-services (Maven): affected all versions; fixed in 18.0.0

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-2021-3424/ (Markdown: https://insights.sbomify.com/CVE-2021-3424/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-3424
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-3424
- OSV: https://osv.dev/vulnerability/CVE-2021-3424

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-3424/
Summaries are generated and may contain mistakes; the official description above is the record.