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.

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.


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