CVE-2026-11800
This JWT algorithm confusion vulnerability in the JWT Authorization Grant flow allows an attacker with valid client credentials to bypass signature verification.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.30%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
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.
- CVSS 3.1
- 8.1 HIGHCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
- EPSS
- 0.30% probability · 23th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-347
- Affected
- redhat/build of keycloak
- Source
- secalert@redhat.com
References
- https://access.redhat.com/errata/RHSA-2026:30083Vendor Advisory
- https://access.redhat.com/errata/RHSA-2026:30084Vendor Advisory
- https://access.redhat.com/security/cve/CVE-2026-11800Vendor Advisory
- https://bugzilla.redhat.com/show_bug.cgi?id=2487006Vendor Advisory
- https://access.redhat.com/errata/RHSA-2026:30083Vendor Advisory
- https://access.redhat.com/errata/RHSA-2026:30084Vendor Advisory
- https://access.redhat.com/security/cve/CVE-2026-11800Vendor Advisory
- https://bugzilla.redhat.com/show_bug.cgi?id=2487006Vendor Advisory
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-11800.jsonVendor Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.