CVE-2026-9801 Keycloak: keycloak: denial of service via malformed ldap password policy response
A remote attacker with high privileges can cause a denial of service by triggering an OutOfMemoryError via a malformed LDAP response.
- Exploited in the wild
- Not known
- Login needed
- An administrator
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-9801?
CVE-2026-9801 is a medium-severity denial of service vulnerability in Redhat Build of Keycloak, published on 28 May 2026. An attacker needs administrator access to exploit it, with no action from the victim.
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.
Weakness: CWE-1284
Which versions are affected by CVE-2026-9801?
2 open source packages ship an affected version, including org.keycloak:keycloak-ldap-federation. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
org.keycloak:keycloak-ldap-federation Maven | All versions | 26.6.3 |
org.keycloak:keycloak-ldap-federation Maven | All versions | 26.6.3 |
Products include Redhat Build of Keycloak.
How do I fix CVE-2026-9801?
Upgrade org.keycloak:keycloak-ldap-federation to 26.6.3 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-9801 being exploited?
There is no known exploitation of CVE-2026-9801 in the wild and no public exploit code.
Other vulnerabilities in Redhat Build of Keycloak
- CVE-2026-15572 Keycloak-services: keycloak-services: dcr protocol mapper type-swap policy bypass allows privilege escalation
- CVE-2026-3047 Keycloak SAML Broken has Authentication Bypass by Primary Weakness
- CVE-2026-15573 Keycloak-services: keycloak-services: authorization bypass via unnormalized uri matching in pathmatcher
- CVE-2026-16102 Keycloak-services: keycloak-services: default dcr policy allows role forgery via user property mappers
- CVE-2026-1609 Org.keycloak/keycloak-quarkus-server: keycloak: unauthorized access via jwt authorization grant with disabled users
Sources
Also known as ECHO-3411-bdf5-a850, GHSA-f6r7-6w34-x2gp, MINI-2qh8-39g9-2wxh, MINI-qhfc-6h7f-hmxc.