# CVE-2024-9666: Org.keycloak/keycloak-quarkus-server: keycloak proxy header handling denial-of-service (dos) vulnerability

> Attackers can cause denial of service in Keycloak by sending malicious proxy headers that trigger expensive DNS lookups, requiring specific proxy trust configurations.

- **Severity:** Medium 4.7 (`CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 25 Nov 2024
- **Updated:** 13 Oct 2026
- **Also known as:** ECHO-7edb-23c5-02ec, GHSA-jgwc-jh89-rpgq

## What is CVE-2024-9666?

CVE-2024-9666 is a medium-severity denial of service vulnerability in Red Hat Build of Keycloak, published on 25 Nov 2024. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

A vulnerability was found in the Keycloak Server. The Keycloak Server is vulnerable to a denial of service (DoS) attack due to improper handling of proxy headers. When Keycloak is configured to accept incoming proxy headers, it may accept non-IP values, such as obfuscated identifiers, without proper validation. This issue can lead to costly DNS resolution operations, which an attacker could exploit to tie up IO threads and potentially cause a denial of service.
The attacker must have access to send requests to a Keycloak instance that is configured to accept proxy headers, specifically when reverse proxies do not overwrite incoming headers, and Keycloak is configured to trust these headers.

Weakness: CWE-444 (Inconsistent Interpretation of HTTP Requests)

## Which versions are affected by CVE-2024-9666?

4 open source packages ship an affected version, including org.keycloak:keycloak-quarkus-server.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `org.keycloak:keycloak-quarkus-server` | Maven | All versions | None |
| `org.keycloak:keycloak-quarkus-server` | Maven | All versions | None |
| `org.keycloak:keycloak-quarkus-server` | Maven | From 25.0.0 | 26.0.6 |
| `org.keycloak:keycloak-quarkus-server` | Maven | From 25.0.0 | 26.0.6 |

## How do I fix CVE-2024-9666?

Upgrade org.keycloak:keycloak-quarkus-server to 26.0.6 or later.

## Is CVE-2024-9666 being exploited?

There is no known exploitation of CVE-2024-9666 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2024-9666 and fix it if it is affected.

What it is: CVE-2024-9666 is a medium-severity denial of service vulnerability in Red Hat Build of Keycloak, published on 25 Nov 2024. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2024-9666 in the wild and no public exploit code.

Affected packages and fixed versions:
- org.keycloak:keycloak-quarkus-server (Maven): affected all versions; no fix listed
- org.keycloak:keycloak-quarkus-server (Maven): affected all versions; no fix listed
- org.keycloak:keycloak-quarkus-server (Maven): affected from 25.0.0; fixed in 26.0.6
- org.keycloak:keycloak-quarkus-server (Maven): affected from 25.0.0; fixed in 26.0.6

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-2024-9666/ (Markdown: https://insights.sbomify.com/CVE-2024-9666/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2024-9666
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-9666
- OSV: https://osv.dev/vulnerability/CVE-2024-9666

---
From sbomify Insights: https://insights.sbomify.com/CVE-2024-9666/
Summaries are generated and may contain mistakes; the official description above is the record.