CVE-2026-11800

Published Jun 25, 2026

Last updated 8 days ago

CVSS high 8.1

Overview

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.
Source
secalert@redhat.com
NVD status
Analyzed
Products
build_of_keycloak

Risk scores

CVSS 3.1

Type
Secondary
Base score
8.1
Impact score
5.2
Exploitability score
2.8
Vector string
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
Severity
HIGH

Weaknesses

secalert@redhat.com
CWE-347
0b0ca135-0b70-47e7-9f44-1890c2a1c46c
CWE-347

Social media

Hype score
Not currently trending

  1. 🚨*CVE* 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 bypas… https://t.co/4j2jzYOCmN ----- Traducción: CVE-2026-11800 Se … https://t.co/utmtNg

    @infoflowcloud

    25 Jun 2026

    30 Impressions

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Configurations

Related CVEs

  1. A flaw was found in Keycloak. A highly privileged user with `manage-clients` permission can exploit this vulnerability by injecting a hardcoded role mapper into any client. This action allows the user to bypass existing scope restrictions and inject the `realm-admin` role into generated tokens, resulting in privilege escalation and full administrative access to the realm.•CVE-2026-4629
  2. A vulnerability was discovered in Keycloak's Admin UI extension that allows certain administrative users to bypass security restrictions. When Fine-Grained Admin Permissions (FGAPv2) are enabled, an administrator who should only be able to search for users (but not view their full details) can use a specific "brute-force-user" endpoint to access a user's full profile. This includes sensitive information and security metadata. The issue occurs because the system fails to check if the administrator has the required "view" permission for that specific user when using this particular search path.•CVE-2026-14209
  3. A flaw was found in the Identity Provider (IdP) mapper component of Keycloak, which is used to manage how user information from external services is mapped to Keycloak users. An administrator with limited permissions to manage identity providers can exploit this flaw by creating a "Hardcoded Role" mapper that assigns high-level administrative roles (like realm-admin) to themselves or others. This allows a restricted administrator to bypass security checks and gain full control over the entire realm.•CVE-2026-12388
  4. A flaw was found in Keycloak Policy Enforcer. This vulnerability allows any authenticated user to bypass all authorization policies, including role, scope, and User-Managed Access (UMA) permission checks. By including the configured access-denied page path within a request URL, either as a path segment or a query parameter, an attacker can gain unauthorized access to protected resources.•CVE-2026-9800
  5. A flaw was found in org.keycloak.authorization. An authenticated user with a granted User-Managed Access (UMA) permission ticket for one resource can exploit this by using a specific permission request prefix to bypass per-resource access control. This allows the user to gain unauthorized access to all resources of that type within the same resource server, even if they do not have a ticket for those specific resources. This vulnerability requires the resource server to be configured in PERMISSIVE policy enforcement mode and affects typed resources with ownerManagedAccess enabled, where no explicit policy protects the resource type. The primary consequence is unauthorized information disclosure or modification of resources.•CVE-2026-9799

References

Sources include official advisories and independent security research.