What’s Vulnerable › Vulnerabilities

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

• Severity: high (CVSS 8.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-06-25 · updated 2026-10-25
• Weakness: CWE-347

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 products

• Red Hat build of Keycloak 26.4: from 26.6 before 26.6.4 — fixed in 26.6.4

How to fix

Upgrade to a fixed version: Red Hat build of Keycloak 26.4 26.6.4. Check the vendor advisory for mitigations.

References

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

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