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Fencer Vulns
medium 5.4

CVE-2026-16093 json

Keycloak-services: keycloak-services: required signed-jwt assertion policy can be bypassed with unsigned assertion headers

published 2026-07-17 3 mo ago modified 2026-09-17 53 d ago also BIT-keycloak-2026-16093 , EUVD-2026-45222

cvss
5.4
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 33%
public exploits
0
none known

Summary

Keycloak provides a mechanism called Client Policies to enforce security requirements on clients, such as requiring them to use signed JWTs for authentication. A flaw was discovered where this enforcement can be bypassed. An attacker with valid client credentials can provide a fake, unsigned assertion header that tricks the system into thinking the policy requirements have been met. This allows the attacker to authenticate using simpler methods like a client secret even when the administrator has mandated more secure, signed assertions.

Patch / fix

  • bitnami keycloak 26.7.3
  • Red Hat Red Hat build of Keycloak 26.6 26.6-20, 26.6.7-3

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-2026-16093 updated cvss 5.4

keycloak-services: keycloak-services: Required signed-JWT assertion policy can be bypassed with unsigned assertion headers

  • 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
    affected: no fix available “Fix deferred”
  • Red Hat build of Keycloak 26.6 rhbk/keycloak-rhel9 26.6-20, rhbk/keycloak-rhel9-operator 26.6-20, rhbk/keycloak-operator-bundle 26.6.7-3
    fixed: vendor fix RHSA-2026:68277
  • Red Hat build of Keycloak 26.6.7
    fixed: vendor fix RHSA-2026:68278

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

0.39% chance of exploitation in the next 30 days, higher than 33% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 5.4 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
OSV 3.1 5.4 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N

Affected packages

ecosystem package affected fixed in
bitnami keycloak
<26.7.3
26.7.3

Affected products

  • Red Hat Red Hat build of Keycloak 26.6
  • Red Hat Red Hat build of Keycloak 26.6.7
  • 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-807 Reliance on Untrusted Inputs in a Security Decision

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.