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Vulnerability record · CVE-2026-11800 · published 25 June 2026

CVE-2026-11800: Redhat build of keycloak improper verification of cryptographic signature vulnerability

Redhat · Build Of Keycloak

A flaw was found in Keycloak. This JWT algorithm confusion vulnerability in the JWT Authorization Grant flow allows an attacker with valid client credentials to bypass signature verification. By forging an assertion, the attacker can create unauthorized access tokens. This enables the attacker to impersonate any federated user linked to the affected Identity Provider, leading to unauthorized access and potential privilege escalation.

8.1 CVSS 3.1 High EPSS 0.30% · top 79.6% CWE-347 · Improper verification of cryptographic signature
8.1CVSS 3.1 base score
0.30%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
9References
15 Jul 2026Last modified by NVD

Description

A flaw was found in Keycloak. This JWT algorithm confusion vulnerability in the JWT Authorization Grant flow allows an attacker with valid client credentials to bypass signature verification. By forging an assertion, the attacker can create unauthorized access tokens. This enables the attacker to impersonate any federated user linked to the affected Identity Provider, leading to unauthorized access and potential privilege escalation.

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://access.redhat.com/errata/RHSA-2026:30083 Vendor Advisory
https://access.redhat.com/errata/RHSA-2026:30084 Vendor Advisory
https://access.redhat.com/security/cve/CVE-2026-11800 Vendor Advisory
https://bugzilla.redhat.com/show_bug.cgi?id=2487006 Vendor Advisory
https://access.redhat.com/errata/RHSA-2026:30083 Vendor Advisory
https://access.redhat.com/errata/RHSA-2026:30084 Vendor Advisory
https://access.redhat.com/security/cve/CVE-2026-11800 Vendor Advisory
https://bugzilla.redhat.com/show_bug.cgi?id=2487006 Vendor Advisory
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-11800.json Vendor Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2026-11800), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.