Keycloak has authentication bypass via jwt algorithm confusion

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

• CISA KEV Not listed.
• EPSS 0.0030, the 22nd percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

1. 3 Nov 2026, 17:24 UTC Confirmed by GitHub Advisory Database
2. 3 Nov 2026, 17:45 UTC Confirmed by OSV

Sources

• GitHub Advisory Database: GHSA-j97h-3f8r-mrjr
• OSV: GHSA-j97h-3f8r-mrjr
• github.com/keycloak/keycloak/security/advisories/GHSA-j97h-3f8r-mrjr
• nvd.nist.gov/vuln/detail/CVE-2026-11800
• github.com/keycloak/keycloak/issues/50357
• github.com/keycloak/keycloak/pull/50374
• github.com/keycloak/keycloak/commit/6d61885f20ac59a2ff8b823fc9ed1f1ef1019951
• github.com/keycloak/keycloak/commit/d343c7373dcc7bfeb9dc14de2309836299c81837
• access.redhat.com/errata/RHSA-2026:30083
• access.redhat.com/errata/RHSA-2026:30084
• access.redhat.com/security/cve/CVE-2026-11800
• bugzilla.redhat.com/show_bug.cgi?id=2487006
• github.com/keycloak/keycloak
• github.com/keycloak/keycloak/releases/tag/26.6.4

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.