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Vulnerability · Published Jun 25, 2026 · Assigned by redhat

CVE-2026-11800Org.keycloak:keycloak-services: keycloak: authentication bypass via jwt algorithm confusion

High 8.1

In plain English

A high-severity security flaw in Red Hat Build of Keycloak from Red Hat. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 23% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)8.1High
Exploit odds (30 days)0.3%top 77.1% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official 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.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Mavenorg.keycloak:keycloak-services26.6.4GHSA-j97h-3f8r-mrjr

Affected products (as reported)

VendorProductVersions
Red Hat Red Hat build of Keycloak 26.6 see references
Red Hat Red Hat build of Keycloak 26.6 see references
Red Hat Red Hat build of Keycloak 26.6 see references
Red Hat Red Hat build of Keycloak 26.6.4 see references
Red Hat Red Hat Build of Keycloak see references
Red Hat Red Hat Build of Keycloak see references
Red Hat Red Hat Data Grid 8 see references
Red Hat Red Hat JBoss Enterprise Application Platform Expansion Pack see references
Red Hat Red Hat Single Sign-On 7 see references

Weakness: CWE-347 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N

References