BlackTreeCVE Intelligence
← Back to the CVE catalogue
Full vulnerability report · 2026
CVE-2026-16100High confidence

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

Red Hat · Red Hat build of Keycloak 26.6

Official source articles: Red Hat RHSA-2026:50848 ↗ · Red Hat RHSA-2026:50849 ↗. Check the applicable product and release in the original source.

6.5MediumCVSS 3.1
Recommended action
Scheduled

Medium technical severity with no CISA KEV confirmation; remediate through the normal risk-based patch cycle unless local exposure raises the priority.

Patch available
R
Operational reassessment

Published severity in operational context

Open reassessment dashboard →
Published severityMediumOperational priority:Medium, unchanged from published severity.unchanged

Evidence used

  • No CISA KEV confirmation is currently recorded.
  • EPSS is 0.55% for the current model date.

Compensating controls

  • Validate the affected product branch and deploy the verified fixed release.
  • Restrict the affected network interface to trusted sources where business-safe.
  • Monitor vendor guidance and exploitation sources for a material change.

Verification

  1. Confirm that the asset runs Red Hat Red Hat build of Keycloak 26.6 and falls inside the recorded affected range.
  2. Verify the installed build against the product-specific fixed version after deployment.
  3. Validate exposure, authentication requirements and compensating controls in the actual environment.
  4. Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Mitigation target: As exposure requiresRemediation target: Within 365 days

This automated reassessment organises public evidence. It does not know asset exposure, business impact or control effectiveness and does not replace CVSS or a human risk decision.

Direct vendor intelligence

Authoritative vendor CSAF and VEX advisories

Structured product status and remediation from the issuing vendor. Product-state explanations are always visible; large lists can be searched or downloaded.

1 current
CVE-2026-16100 · CSAF 2.0 · revision 3 · finalRed Hat Product Securitykeycloak-services: keycloak-services: Unbounded metric cardinality in user event metrics via request-controlled error text
10 fixed

The vendor explicitly identifies these products or versions as containing the fix.

  • rhbk/keycloak-operator-bundle@sha256:06ee2f18c4218c9a095360efa2023b2080aa81e04a08363dbcb1d14de85a5d0d_amd64 as a component of Red Hat build of Keycloak 26.6
  • rhbk/keycloak-rhel9-operator@sha256:0024d9a0b69b61004a0d35ee25eefc443fe75ce2563b1645ec318caacc0aa23c_s390x as a component of Red Hat build of Keycloak 26.6
  • rhbk/keycloak-rhel9-operator@sha256:2eeef9cec3ee8e3cfdb1c4b7377582b4a5378f852e11872eeb74597ad9ec0615_amd64 as a component of Red Hat build of Keycloak 26.6
  • rhbk/keycloak-rhel9-operator@sha256:37c7d8c5b4bd9649b3da2c0929075c6bd311361667a7eb25eb3f52927b7eca8e_ppc64le as a component of Red Hat build of Keycloak 26.6
  • rhbk/keycloak-rhel9-operator@sha256:aadf59a1eeb8e64f2f1eea906dd1837fd144d8406b07630a3e2b0c9265c107e7_arm64 as a component of Red Hat build of Keycloak 26.6
  • rhbk/keycloak-rhel9@sha256:30a9118cf874444aabdf4dd8f84d44cb503f89d8432a652fbb0ba860d3815c4d_ppc64le as a component of Red Hat build of Keycloak 26.6
  • rhbk/keycloak-rhel9@sha256:7b668bfd2a9a1bd6343fb2e802912eaa72bd7043fa5be6e0a6edc06894c74b63_arm64 as a component of Red Hat build of Keycloak 26.6
  • rhbk/keycloak-rhel9@sha256:83e1c37e7e5b268c8b516f9c13d064db4fbdcd68d25a542dec0d237665b06705_amd64 as a component of Red Hat build of Keycloak 26.6
  • rhbk/keycloak-rhel9@sha256:c8203365ded9864afe84f579798eefd5f4a79ee6a4e585e47fcb0d8ea3ce959f_s390x as a component of Red Hat build of Keycloak 26.6
  • Red Hat build of Keycloak 26.6.5
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.
Remediation
Before applying the update, back up your existing installation, including all applications, configuration files, databases and database settings, and so on.
Optional official sources

National CERT insights
?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.

Choose official national sources for this report. Each advisory shows its original language. Your selection is remembered on this device and included in shared links.

Official European source

ENISA European Vulnerability Database

Official EUVD identifiers, advisory evidence and known-exploited context. Missing fields are not treated as evidence of low risk.

1 current
ENISA EUVD identifier

EUVD-2026-53384

No EUVD known-exploited evidence

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.

EUVD state
Present in the current official mapping
Known exploitation
Not present in the current ENISA EUVD known-exploited dataset. This is not proof of no exploitation.
ENISA score
6.5 · CVSS 3.1
Advisory evidence
No linked advisory details stored yet
Recommended actionScheduled

Medium technical severity with no CISA KEV confirmation; remediate through the normal risk-based patch cycle unless local exposure raises the priority.

Patch available
01

What, why and how

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.

What

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.

Why

The product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.

How

An attacker operating through a network path may attempt exploitation with low privileges. If successful, the issue may disrupt the affected service.

What

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.

Why

The product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.

How

An attacker operating through a network path may attempt exploitation with low privileges. If successful, the issue may disrupt the affected service.

02

Exploit reality and attack path

CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.

Observed exploitation
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
No confirmed evidence

No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.

Public PoC / exploit material
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
None recorded

No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.

Likely attack path
a network path → Allocation of Resources Without Limits or Throttling → disrupt the affected service
Attack surface
Network
Privileges required
Low: a basic authenticated account is required
User interaction
None
Attack complexity
Low: no specialised conditions are recorded
Security boundary
Unchanged: impact remains within the vulnerable component's security authority
Weakness
?CWE means Common Weakness Enumeration: a standard category for the underlying weakness.
CWE-770 ↗

CWE-770: Allocation of Resources Without Limits or Throttling. The product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.

CVSS vector
?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Common Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.

AVNetworkAttack vector: The vulnerable component can be reached over a network.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.PRLowPrivileges required: The attacker needs basic user-level privileges.UINoneUser interaction: No action by another user is required.SUnchangedScope: The security impact remains within the vulnerable component's authority.CNoneConfidentiality impact: No direct loss is represented by this metric.INoneIntegrity impact: No direct loss is represented by this metric.AHighAvailability impact: A successful attack can cause a major loss.
Post-exploitation / living off the land
No specific living-off-the-land technique is confirmed in the structured sources. Monitor normal administration tools for activity inconsistent with the affected service's baseline.
NetworkDenial of serviceCWE-770
A

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

ENISA EUVD · EUVD-2026-53384Official EUVD mapping

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.

Official EUVD record ↗
BSI · German · WID-SEC-2026-2677RedHat Build of Keycloak: Mehrere Schwachstellen

Ein Angreifer kann mehrere Schwachstellen in Keycloak ausnutzen, um Administratorrechte zu erlangen, Benutzerkonten zu übernehmen, Sicherheitsmaßnahmen zu umgehen, vertrauliche Informationen offenzulegen, Daten zu manipulieren oder einen Denial-of-Service-Zustand herbeizuführen.

Official advisory ↗
Cyber Security Agency of Singapore · English · CSA-SB-20260812Security Bulletin 12 Aug 2026

The Cyber Security Agency of Singapore included this CVE in its official Security Bulletin 12 Aug 2026, published on 12 August 2026. Open the linked bulletin for the product, severity and reference information published in that issue.

Official advisory ↗
CERT-FR · French · CERTFR-2026-AVI-0976Multiples vulnérabilités dans KeyCloak

De multiples vulnérabilités ont été découvertes dans KeyCloak. Certaines d'entre elles permettent à un attaquant de provoquer une élévation de privilèges, un déni de service à distance et une atteinte à la confidentialité des données.

Official advisory ↗
JVN iPedia · Japanese · JVNDB-2026-027802レッドハットのbuild of keycloakにおける制限またはスロットリング無しのリソースの割り当てに関する脆弱性

Keycloakのユーザーイベントメトリクス記録に脆弱性が発見されました。メトリクスが有効になっている場合、システムは失敗したアカウント操作からの生のエラーメッセージをPrometheusのメトリクスラベルとして記録します。これらのエラーメッセージには存在しないクライアントIDなどのユーザー提供の入力が含まれている可能性があるため、認証済みユーザーが大量のユニークなメトリクスエントリを作成し、最終的にシステムメモリを枯渇させてサービスがクラッシュしたり利用不能になったりする恐れがあります。

Official advisory ↗
03

Patch and workaround

Operational remediation based on structured source evidence.

Status
?Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change.
Patch available
Affected
Red Hat build of Keycloak 26.6: patch: 26.6.5-1, patch: 26.6-11
Fixed
Action
Before applying the update, back up your existing installation, including all applications, configuration files, databases and database settings, and so on.
Workaround
No verified workaround is recorded. If business-safe, reduce exposure to the affected interface and allow only trusted sources until authoritative guidance is available.
Official vendor articles3 stored documents

Linked articles are downloaded and versioned as source evidence. A CVE mention or approved update relationship does not, by itself, verify a fix for every product branch.

  • Vendor release notes →Original publisher ↗Searchable text snapshot · Captured 29 Sep 2026Red Hat Product Errata RHSA-2026:50848 - Security Advisory Issued: 2026-08-05 Updated: 2026-08-05 RHSA-2026:50848 - Security Advisory Overview Synopsis Important: Red Hat build of Keycloak 26.6.5 Security Update Type/Severity Security Advisory: Important Topic New Red Hat build of Keycloak 26.6.5 packages are ava
  • Vendor release notes →Original publisher ↗Searchable text snapshot · Captured 29 Sep 2026Red Hat Product Errata RHSA-2026:50849 - Security Advisory Issued: 2026-08-05 Updated: 2026-08-05 RHSA-2026:50849 - Security Advisory Overview Updated Images Synopsis Important: Red Hat build of Keycloak 26.6.5 Images Security Update Type/Severity Security Advisory: Important Topic New images are available for R
  • CVE-2026-16100 - Red Hat Customer Portal →Original publisher ↗Searchable text snapshot · Captured 28 Sep 2026CVE-2026-16100 Description 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 authentica
04

Evidence and provenance

Published 5 Aug 2026 · Last source change 31 Aug 2026, 15:01 UTC · CWE-770 · Allocation of Resources Without Limits or Throttling

CVE recordCVE.org · 5.2
CVSS sourceCNA
EPSS source
?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.
FIRST · tracked since 2026-08-14
European sourceENISA EUVD · EUVD-2026-53384
Product sourceCNA
Remediation sourceVendor CSAF · Red Hat Product Security
CWE sourceCNA
NVD statusNVD modified after enrichment

Missing structured fields: affected versions. Missing data is not evidence of low risk; review the primary advisory.

Material change intelligence

What changed after publication

View recent updates ↗
  1. Affected versionsThe structured affected or fixed version information changed.
    Before
    See the vendor and CVE records for the affected range. · Fixed: 26.6.5-1 < *; 26.6-11 < *
    After
    See the vendor and CVE records for the affected range. · Fixed: Red Hat build of Keycloak 26.6: 26.6.5-1 < *, 26.6-11 < *
    CNA ↗
Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
Fixed release or patch reference recorded
ENISA EUVD · EUVD-2026-53384↗Vendor advisory↗CVE authority or vendor reference · Red Hat RHSA-2026:50848↗Vendor advisory · Red Hat RHSA-2026:50849↗Vendor advisory↗Official CVE record (CNA and ADP data)↗NVD record↗
Technical terms and abbreviations used in this report
CVE
Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
CVSS
Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
EPSS
Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
CWE
Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
CNA
CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
CISA ADP
Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
NVD
National Vulnerability Database: NIST's enrichment service for CVE records.
CERT / CSIRT
A computer security incident response team that publishes warnings or coordinates incident response.
PoC
Proof of concept: public material that demonstrates or helps reproduce exploitation.
CSAF
Common Security Advisory Framework: a machine-readable format for security advisories.
LoTL
Living off the land: abuse of legitimate tools or system functions during an attack.
Free version - for non-commercial use only.CVE-2026-16100 · cve.blacktree.nl