Keycloak: keycloak: denial of service via malformed ldap password policy response
Summary
| CVE | CVE-2026-9801 |
|---|---|
| State | PUBLISHED |
| Assigner | redhat |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-05-28 06:16:29 UTC |
| Updated | 2026-05-28 13:44:54 UTC |
| 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. |
Risk And Classification
Primary CVSS: v3.1 4.9 MEDIUM from [email protected]
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
EPSS: 0.002840000 probability, percentile 0.519280000 (date 2026-06-01)
Problem Types: CWE-1284 | CWE-1284 Improper Validation of Specified Quantity in Input
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 3.1 | [email protected] | Primary | 4.9 | MEDIUM | CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H |
| 3.1 | CNA | CVSS | 4.9 | MEDIUM | CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H |
CVSS v3.1 Breakdown
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Red Hat | Red Hat Build Of Keycloak | Not specified | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| bugzilla.redhat.com/show_bug.cgi | [email protected] | bugzilla.redhat.com | |
| access.redhat.com/security/cve/CVE-2026-9801 | [email protected] | access.redhat.com | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: Red Hat would like to thank Seongkuk Park for reporting this issue. (en)
Additional Advisory Data
| Source | Time | Event |
|---|---|---|
| CNA | 2026-05-28T04:00:39.339Z | Reported to Red Hat. |
| CNA | 2026-05-28T04:18:25.872Z | Made public. |
Workarounds
CNA: 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.