CVE-2026-18967

Keycloak-services: keycloak-services: saml onetimeuse assertion replay in idp-initiated broker flow

Published Aug 6, 2026 CVSS 3.1 · 6.4 Medium EPSS < 1% KEV · Not listed
Description
A flaw was found in the SAML broker component of Keycloak, an identity and access management solution. When configured as a SAML broker using the IdP-Initiated flow, Keycloak fails to enforce the OneTimeUse condition in SAML assertions. This allows an attacker who captures a valid, unused assertion to replay it multiple times. Successful exploitation could allow an attacker to hijack a user's session and gain unauthorized access to the system as that user.

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.

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
First Time appeared Redhat build Of Keycloak
Redhat jboss Enterprise Application Platform Expansion Pack
Redhat single Sign-on
Vendors & Products Redhat build Of Keycloak
Redhat jboss Enterprise Application Platform Expansion Pack
Redhat single Sign-on
Type Values Removed Values Added
Metrics ssvc

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

Type Values Removed Values Added
Description A flaw was found in the SAML broker component of Keycloak, an identity and access management solution. When configured as a SAML broker using the IdP-Initiated flow, Keycloak fails to enforce the OneTimeUse condition in SAML assertions. This allows an attacker who captures a valid, unused assertion to replay it multiple times. Successful exploitation could allow an attacker to hijack a user's session and gain unauthorized access to the system as that user.
Title Keycloak-services: keycloak-services: saml onetimeuse assertion replay in idp-initiated broker flow
First Time appeared Redhat
Redhat build Keycloak
Redhat jbosseapxp
Redhat red Hat Single Sign On
Weaknesses CWE-294
CPEs cpe:/a:redhat:build_keycloak:
cpe:/a:redhat:jbosseapxp
cpe:/a:redhat:red_hat_single_sign_on:7
Vendors & Products Redhat
Redhat build Keycloak
Redhat jbosseapxp
Redhat red Hat Single Sign On
References
Metrics cvssV3_1

{'score': 6.4, 'vector': 'CVSS:3.1/AV:A/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
redhat
Published
Updated
Aug 6, 2026, 5:31 PM
Reserved
Aug 5, 2026, 3:22 PM
Status
Analyzed
Published
Aug 6, 2026, 7:16 AM
Modified
Aug 10, 2026, 7:15 PM
Severity
Moderate
Public date
Jul 31, 2026, 2:42 PM