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

CVE-2026-9801 · Severity: medium · CVSS 4.9 · Published 2026-05-28

Keycloak, a popular identity and access management solution, is vulnerable to a denial-of-service attack when integrated with LDAP directory services. An attacker with administrative privileges or control over a connected LDAP server can send a specially crafted response that causes the Keycloak server to run out of memory and crash. This results in a complete service outage for all users and applications relying on the affected Keycloak instance for authentication.

Technologies: Keycloak, org.keycloak:keycloak-ldap-federation (Maven), Red Hat build of Keycloak. Vendors: Keycloak, Maven, Red Hat.

Quick answers

Is CVE-2026-9801 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-9801 being exploited in the wild.
How severe is CVE-2026-9801?
Medium severity, with a CVSS score of 4.9, published 28 May 2026.
Which products and versions are affected?
Keycloak < 26.6.3; Keycloak-Ldap-Federation < 26.6.3; org.keycloak:keycloak-ldap-federation (Maven) < 26.6.3, ECOSYSTEM:introduced=0,fixed=26.6.3; Red Hat build of Keycloak 26.4, 26.6.
Is there a fix for CVE-2026-9801?
Yes. org.keycloak:keycloak-ldap-federation (Maven): upgrade to 26.6.3 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-9801 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-9801?
Check whether you run Keycloak, Keycloak-Ldap-Federation, org.keycloak:keycloak-ldap-federation (Maven) or one of the others listed at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • org.keycloak:keycloak-ldap-federation (Maven): upgrade to 26.6.3 or later
    # set org.keycloak:keycloak-ldap-federation to 26.6.3 in your pom.xml or build.gradle

Technical details

A vulnerability exists in the Keycloak LDAP federation provider (org.keycloak:keycloak-ldap-federation) due to improper validation of specified quantities in input (CWE-1284). A remote attacker with high privileges (such as a realm administrator) or an attacker who has compromised an upstream LDAP server can exploit this by sending a malformed LDAP password policy response during an authentication request. This malformed input triggers an OutOfMemoryError within the Java Virtual Machine (JVM), causing the process to terminate and resulting in a denial of service for all realms on the node. The issue is fixed in Keycloak version 26.6.3.

Affected products

  • Keycloak Keycloak < 26.6.3
  • Keycloak keycloak-ldap-federation < 26.6.3
  • Red Hat Red Hat build of Keycloak 26.4, 26.6

Identifiers

  • CVE-2026-9801
  • GHSA-f6r7-6w34-x2gp

Timeline

  • 2026-05-28: disclosed
  • 2026-05-28: advisory
  • 2026-06-10: patched: Red Hat security advisory issued

References

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