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Fencer Vulns
medium 6.4

CVE-2026-18967 json

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

published 2026-08-06 3 mo ago modified 2026-08-10 2 mo ago also EUVD-2026-53716

cvss
6.4
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 14%
public exploits
0
none known

Summary

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.

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-2026-18967 updated cvss 6.4

keycloak-services: keycloak-services: SAML OneTimeUse assertion replay in IdP-Initiated broker flow

  • Red Hat Build of Keycloak rhbk-keycloak-rhel9, rhbk-openshift-rhel9, keycloak-services 26.6.4.redhat-00004
    affected: workaround, no fix available
  • Red Hat JBoss Enterprise Application Platform Expansion Pack keycloak-services 26.6.4.redhat-00004
    affected: workaround, no fix available “Fix deferred”
  • Red Hat Single Sign-On 7 keycloak-services 26.6.4.redhat-00004
    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
total
Assessed
3 mo ago

Exploit prediction

0.23% chance of exploitation in the next 30 days, higher than 14% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 6.4 CVSS:3.1/AV:A/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N
NVD 3.1 8.1 CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Affected products

  • Red Hat Red Hat Build of Keycloak
  • Red Hat Red Hat JBoss Enterprise Application Platform Expansion Pack
  • Red Hat Red Hat Single Sign-On 7

Classification

Weakness
  • CWE-294 Authentication Bypass by Capture-replay

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.