# CVE-2021-3827: ECP SAML binding bypasses authentication flows

> Attackers can bypass MFA authentication in Keycloak by exploiting the default ECP binding flow with crafted SOAP requests.

- **Severity:** Medium 6.8 (`CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 23 Aug 2022
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-4pc7-vqv5-5r3v

## What is CVE-2021-3827?

CVE-2021-3827 is a medium-severity authentication bypass vulnerability in Redhat Keycloak, published on 23 Aug 2022. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

A flaw was found in keycloak, where the default ECP binding flow allows other authentication flows to be bypassed. By exploiting this behavior, an attacker can bypass the MFA authentication by sending a SOAP request with an AuthnRequest and Authorization header with the user's credentials. The highest threat from this vulnerability is to confidentiality and integrity.

Weakness: CWE-287 (Improper Authentication)

## Which versions are affected by CVE-2021-3827?

2 open source packages ship an affected version, including org.keycloak:keycloak-saml-core. It affects 3 products.


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

Products: Redhat Keycloak, Redhat Openshift Container Platform, Redhat Single Sign-On.

## How do I fix CVE-2021-3827?

Upgrade org.keycloak:keycloak-saml-core to 18.0.0 or later.

## Is CVE-2021-3827 being exploited?

There is no known exploitation of CVE-2021-3827 in the wild and no public exploit code.

## 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-2021-3827 and fix it if it is affected.

What it is: CVE-2021-3827 is a medium-severity authentication bypass vulnerability in Redhat Keycloak, published on 23 Aug 2022. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-3827 in the wild and no public exploit code.

Affected packages and fixed versions:
- org.keycloak:keycloak-saml-core (Maven): affected all versions; fixed in 18.0.0
- org.keycloak:keycloak-saml-core (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-2021-3827/ (Markdown: https://insights.sbomify.com/CVE-2021-3827/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-3827
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-3827
- OSV: https://osv.dev/vulnerability/CVE-2021-3827

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-3827/
Summaries are generated and may contain mistakes; the official description above is the record.