---
id: CVE-2024-9666
title: A vulnerability was found in the Keycloak Server
summary: >-
  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 accep…
severity: medium
cvss: 4.7
cvssVector: 'CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H'
cwe:
  - CWE-444
vendor: Red Hat
product: keycloak
affected:
  - keycloak < 24.0.9
  - keycloak >= 25.0.0 < 26.0.6
  - rhbk/keycloak-operator-bundle (all versions)
  - rhbk/keycloak-rhel9 (all versions)
  - rhbk/keycloak-rhel9-operator (all versions)
  - build_of_keycloak_24.0.9
  - rhbk/keycloak-operator-bundle (all versions)
  - rhbk/keycloak-rhel9 (all versions)
  - rhbk/keycloak-rhel9-operator (all versions)
  - build_of_keycloak_26.0.6
  - keycloak-quarkus-server (all versions)
  - keycloak-quarkus-server
published: '2024-11-25'
updated: '2026-09-21'
sourceUpdated: '2026-09-21T06:16:59.443'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2024-9666'
references:
  - url: 'https://access.redhat.com/errata/RHSA-2024:10175'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/errata/RHSA-2024:10176'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/errata/RHSA-2024:10177'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/errata/RHSA-2024:10178'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/security/cve/CVE-2024-9666'
    label: secalert@redhat.com
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2317440'
    label: secalert@redhat.com
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2024/cve-2024-9666.json
  - url: 'https://www.cve.org/CVERecord?id=CVE-2024-9666'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2024-9666'
tags:
  - nvd
  - cve.org
  - csaf
  - vex
  - red-hat
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2024-11-25T17:14:55.721958Z'
epss: 0.00399
epssPercentile: 0.34
ingestedAt: '2026-08-04T08:38:41.180Z'
patched:
  - build_of_keycloak 24
  - build_of_keycloak 26.0
  - build_of_keycloak 24.0.9
  - build_of_keycloak 26.0.6
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

## Vendor advisories

- **RHSA-2024:10175** · Red Hat · fixed in: Red Hat build of Keycloak 24 · released 2024-11-21 · [advisory](https://access.redhat.com/errata/RHSA-2024:10175)
- **RHSA-2024:10177** · Red Hat · fixed in: Red Hat build of Keycloak 26.0 · released 2024-11-21 · [advisory](https://access.redhat.com/errata/RHSA-2024:10177)
- **RHSA-2024:10176** · Red Hat · fixed in: Red Hat build of Keycloak 24.0.9 · released 2024-11-21 · [advisory](https://access.redhat.com/errata/RHSA-2024:10176)
- **RHSA-2024:10178** · Red Hat · fixed in: Red Hat build of Keycloak 26.0.6 · released 2024-11-21 · [advisory](https://access.redhat.com/errata/RHSA-2024:10178)
- **Red Hat VEX** · Low · affected: Red Hat Build of Keycloak · no fix planned: Red Hat Build of Keycloak · updated 2026-09-21 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2024/cve-2024-9666.json)