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Vulnerability · Published May 28, 2026 · Assigned by redhat

CVE-2026-9801Keycloak: keycloak: denial of service via malformed ldap password policy response

Medium 4.9

In plain English

A medium-severity security flaw in Red Hat build of Keycloak 26.4 from Red Hat. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 41% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)4.9Medium
Exploit odds (30 days)0.5%top 58.6% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official 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.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Mavenorg.keycloak:keycloak-ldap-federation26.6.3GHSA-f6r7-6w34-x2gp

Affected products (as reported)

VendorProductVersions
Red Hat Red Hat build of Keycloak 26.4 see references
Red Hat Red Hat build of Keycloak 26.4 see references
Red Hat Red Hat build of Keycloak 26.4 see references
Red Hat Red Hat build of Keycloak 26.4.13 see references
Red Hat Red Hat build of Keycloak 26.6 see references
Red Hat Red Hat build of Keycloak 26.6 see references
Red Hat Red Hat build of Keycloak 26.6 see references
Red Hat Red Hat build of Keycloak 26.6.3 see references

Weakness: CWE-1284 · Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H

References