CVE-2026-11800
High
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.
SeverityHigh
CVSS8.1
Exploit probability—
Product
Redhat Build Of Keycloak
PublishedJun 25, 2026
First seenJun 25, 2026
Weakness typeCWE-347CWE-347
How to fix
Update
- redhat build_of_keycloak26.6.4 or later
- org.keycloak:keycloak-services26.6.4 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| redhat build_of_keycloak | 26.6 ≤ v < 26.6.4 | 26.6.4 |
| org.keycloak:keycloak-servicesMaven | v < 26.6.4 | 26.6.4 |
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