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Fencer Vulns
medium 6.5

CVE-2026-16100 json

Keycloak-services: keycloak-services: unbounded metric cardinality in user event metrics via request-controlled error text

published 2026-08-05 3 mo ago modified 2026-09-08 2 mo ago also BIT-keycloak-2026-16100 , EUVD-2026-53384

cvss
6.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.6%
EPSS 0.6% chance of exploitation in 30 days, percentile 46%
public exploits
0
none known

Summary

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.

Patch / fix

  • bitnami keycloak 26.6.5
  • Red Hat Red Hat build of Keycloak 26.6 26.6-11, 26.6.5-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-16100 updated cvss 6.5

keycloak-services: keycloak-services: Unbounded metric cardinality in user event metrics via request-controlled error text

  • Red Hat build of Keycloak 26.6 rhbk/keycloak-rhel9 26.6-11, rhbk/keycloak-rhel9-operator 26.6-11, rhbk/keycloak-operator-bundle 26.6.5-1
    fixed: vendor fix RHSA-2026:50849
  • Red Hat build of Keycloak 26.6.5
    fixed: vendor fix RHSA-2026:50848
  • Red Hat Data Grid 8 keycloak-services 23.0.7 Red Hat JBoss Enterprise Application Platform Expansion Pack keycloak-services 23.0.7 Red Hat Single Sign-On 7 keycloak-services 23.0.7
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
3 mo ago

Exploit prediction

0.55% chance of exploitation in the next 30 days, higher than 46% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
OSV 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected packages

ecosystem package affected fixed in
bitnami keycloak
>=26.6.0, <26.6.5
26.6.5

Affected products

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

Classification

Weakness
  • CWE-770 Allocation of Resources Without Limits or Throttling

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.