CVE-2026-11800

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 v3 8.1 HIGH

8.1^/10

CVSS v3 : HIGH

Vector :

Exploitability : 2.8 / Impact : 5.2

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required LOW

User Interaction NONE

Confidentiality Impact HIGH

Integrity Impact HIGH

Availability Impact NONE

Scope UNCHANGED

References

Link	Resource
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

Configurations

Configuration 1 (hide)

cpe:2.3:a:redhat:build_of_keycloak:*:*:*:*:*:*:*:*

History

25 Oct 2026, 22:10

Type	Values Removed	Values Added
Summary		(es) Se encontró un fallo en Keycloak. Esta vulnerabilidad de confusión de algoritmo JWT en el flujo de concesión de autorización JWT permite a un atacante con credenciales de cliente válidas eludir la verificación de firma. Al falsificar una aserción, el atacante puede crear tokens de acceso no autorizados. Esto permite al atacante suplantar a cualquier usuario federado vinculado al Proveedor de Identidad afectado, lo que lleva a un acceso no autorizado y una potencial escalada de privilegios.

Information

Published : 2026-06-25 22:17

Updated : 2026-10-25 22:10

NVD link : CVE-2026-11800

Mitre link : CVE-2026-11800

CVE.ORG link : CVE-2026-11800

JSON object : View

Products Affected

redhat

build_of_keycloak

CWE

CWE-347

Improper Verification of Cryptographic Signature

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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."}, {"lang": "es", "value": "Se encontr\u00f3 un fallo en Keycloak. Esta vulnerabilidad de confusi\u00f3n de algoritmo JWT en el flujo de concesi\u00f3n de autorizaci\u00f3n JWT permite a un atacante con credenciales de cliente v\u00e1lidas eludir la verificaci\u00f3n de firma. Al falsificar una aserci\u00f3n, el atacante puede crear tokens de acceso no autorizados. Esto permite al atacante suplantar a cualquier usuario federado vinculado al Proveedor de Identidad afectado, lo que lleva a un acceso no autorizado y una potencial escalada de privilegios."}], "lastModified": "2026-10-25T22:10:00.150", "configurations": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:a:redhat:build_of_keycloak:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "EC1CC78D-43C0-4F1E-AC80-6B302F992816", "versionEndExcluding": "26.6.4", "versionStartIncluding": "26.6"}], "operator": "OR"}]}], "sourceIdentifier": "secalert@redhat.com"}