A flaw was found in Keycloak. A remote attacker with high privileges, such as a realm administrator configuring a malicious Lightweight Directory Access Protocol (LDAP) server or an attacker compromising an upstream LDAP server, could exploit this vulnerability. By sending a malformed LDAP password policy response during a password authentication request, the attacker can trigger an OutOfMemoryError. This causes the Keycloak Java Virtual Machine (JVM) to terminate, leading to a denial of service (DoS) for all realms on the affected node.

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Advisories

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Fixes

Solution

No solution given by the vendor.


Workaround

To mitigate this vulnerability, ensure that Keycloak's LDAP user-storage providers are configured to connect only to trusted and secure LDAP servers. Avoid configuring LDAP federation with unverified or potentially malicious LDAP endpoints. Additionally, always use TLS for LDAP connections to prevent Man-in-the-Middle attacks. If an upstream LDAP server is compromised, it should be isolated and secured immediately.

History

Sat, 30 May 2026 02:15:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Thu, 28 May 2026 12:15:00 +0000

Type Values Removed Values Added
References
Metrics threat_severity

None

threat_severity

Moderate


Thu, 28 May 2026 09:45:00 +0000

Type Values Removed Values Added
First Time appeared Redhat build Of Keycloak
Vendors & Products Redhat build Of Keycloak

Thu, 28 May 2026 06:00:00 +0000

Type Values Removed Values Added
Description A flaw was found in Keycloak. A remote attacker with high privileges, such as a realm administrator configuring a malicious Lightweight Directory Access Protocol (LDAP) server or an attacker compromising an upstream LDAP server, could exploit this vulnerability. By sending a malformed LDAP password policy response during a password authentication request, the attacker can trigger an OutOfMemoryError. This causes the Keycloak Java Virtual Machine (JVM) to terminate, leading to a denial of service (DoS) for all realms on the affected node.
Title Keycloak: keycloak: denial of service via malformed ldap password policy response
First Time appeared Redhat
Redhat build Keycloak
Weaknesses CWE-1284
CPEs cpe:/a:redhat:build_keycloak:
Vendors & Products Redhat
Redhat build Keycloak
References
Metrics cvssV3_1

{'score': 4.9, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H'}


Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: redhat

Published:

Updated: 2026-05-30T01:54:07.920Z

Reserved: 2026-05-28T04:00:46.722Z

Link: CVE-2026-9801

cve-icon Vulnrichment

Updated: 2026-05-30T01:54:02.946Z

cve-icon NVD

Status : Undergoing Analysis

Published: 2026-05-28T06:16:29.493

Modified: 2026-05-28T13:44:54.327

Link: CVE-2026-9801

cve-icon Redhat

Severity : Moderate

Publid Date: 2026-05-28T04:18:25Z

Links: CVE-2026-9801 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-05-28T09:30:05Z

Weaknesses