CVE-2026-92855

Keycloak-services: keycloak-services: saml broker accepts holder-of-key assertions without proof of key possession

Published Nov 5, 2026 CVSS 3.1 · 7.4 High EPSS < 1% KEV · Not listed
Description
A flaw was found in the SAML identity broker component of Keycloak, which is used to delegate authentication to external identity providers. The issue occurs because the broker fails to verify that a user actually possesses the private key associated with a holder-of-key assertion. An attacker who intercepts a victim signed assertion can replay it to gain unauthorized access and impersonate the victim without needing their private key.

Remediation

Vendor Workaround

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability. --- CME Mitigation Guidance (2026-11-06) --- Disclaimer: The following mitigation solutions are provided as a courtesy, pending the application of an official patch. This content was generated utilizing AI tools in conjunction with data from https://cmetaxonomy.org. Customers are advised to independently evaluate and test these temporary mitigations within their own infrastructure. The highest-value action is to enforce proof of possession for bound keys in SAML identity broker subject-confirmation validation: upgrade to Keycloak 26.4.17 / 26.6.8 (or the corresponding fixed Red Hat builds), which enforce proof of possession for the bound key or reject assertions that contain only unvalidated holder-of-key confirmations, closing replaying intercepted SAML holder-of-key assertions. Until patched, this is a concern on Keycloak deployments configured as a SAML identity broker trusting upstream providers that issue holder-of-key assertions, so restrict and audit trusted upstream SAML identity providers issuing holder-of-key assertions to prevent interception and unauthorized replay of signed assertions. As a compensating measure, enforce mandatory secondary authentication factor in Keycloak post-federation to block login completion on replayed assertions. These controls limit blast radius and contain exploitation, but they do not fix the underlying missing proof-of-possession verification flaw — apply the upstream patch to fully remediate. Highest-impact CME: CME-801 Multi-Factor Authentication (MFA) (medium)

Tracking

Sign in to view the affected projects.

Advisories

No advisories available
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Type Values Removed Values Added
CPEs cpe:/a:redhat:build_keycloak: cpe:/a:redhat:build_keycloak:26.4::el9
cpe:/a:redhat:build_keycloak:26.6::el9
References
Type Values Removed Values Added
First Time appeared Red Hat
Red Hat red Hat Build Of Keycloak 26.4
Redhat build Of Keycloak
Redhat single Sign-on
Vendors & Products Red Hat
Red Hat red Hat Build Of Keycloak 26.4
Redhat build Of Keycloak
Redhat single Sign-on
Type Values Removed Values Added
Description A flaw was found in the SAML identity broker component of Keycloak, which is used to delegate authentication to external identity providers. The issue occurs because the broker fails to verify that a user actually possesses the private key associated with a holder-of-key assertion. An attacker who intercepts a victim signed assertion can replay it to gain unauthorized access and impersonate the victim without needing their private key.
Title Keycloak-services: keycloak-services: saml broker accepts holder-of-key assertions without proof of key possession
First Time appeared Redhat
Redhat build Keycloak
Redhat red Hat Single Sign On
Weaknesses CWE-287
CPEs cpe:/a:redhat:build_keycloak:
cpe:/a:redhat:red_hat_single_sign_on:7
Vendors & Products Redhat
Redhat build Keycloak
Redhat red Hat Single Sign On
References
Metrics cvssV3_1

{'score': 7.4, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
redhat
Published
Updated
Nov 9, 2026, 10:24 PM
Reserved
Sep 17, 2026, 4:51 AM
Status
Awaiting Analysis
Published
Nov 5, 2026, 6:17 PM
Modified
Nov 9, 2026, 11:17 PM
Severity
Important
Public date
Nov 5, 2026, 12:00 AM