Keycloak Prometheus Metric Label DoS via Memory Exhaustion
CVE-2026-16100 Published on August 5, 2026

Keycloak-services: keycloak-services: unbounded metric cardinality in user event metrics via request-controlled error text
A flaw was found in the user-event metrics recording of Keycloak. When metrics are enabled, the system records raw error messages from failed account operations as Prometheus metric labels. Because these error messages can include user-supplied input like nonexistent client IDs, an authenticated user can create a massive number of unique metric entries, eventually exhausting system memory and causing the service to crash or become unavailable.

Vendor Advisory Vendor Advisory NVD

Vulnerability Analysis

CVE-2026-16100 is exploitable with network access, and requires small amount of user privileges. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality and integrity, and a high impact on availability.

Attack Vector:
NETWORK
Attack Complexity:
LOW
Privileges Required:
LOW
User Interaction:
NONE
Scope:
UNCHANGED
Confidentiality Impact:
NONE
Integrity Impact:
NONE
Availability Impact:
HIGH

Timeline

Reported to Red Hat.

Made public. 22 days later.

Weakness Type

Allocation of Resources Without Limits or Throttling

The software allocates a reusable resource or group of resources on behalf of an actor without imposing any restrictions on the size or number of resources that can be allocated, in violation of the intended security policy for that actor.


Products Associated with CVE-2026-16100

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Red Hat Build Keycloak
 
Red Hat Jboss Data Grid
 
Red Hat Jbosseapxp
 
Red Hat Single Sign On
 

Affected Versions

Red Hat build of Keycloak 26.6: Red Hat build of Keycloak 26.6: Red Hat build of Keycloak 26.6: Red Hat build of Keycloak 26.6.5: Red Hat build of Keycloak 26.6.5: Red Hat build of Keycloak 26.6.5: Red Hat Data Grid 8: Red Hat JBoss Enterprise Application Platform Expansion Pack: Red Hat Single Sign-On 7: