Review reviewHigh

CVE-2026-9704

Red Hat Red Hat build of Keycloak 26.4, Red Hat build of Keycloak 26.4.13, Red Hat build of Keycloak 26.6

A flaw was found in Keycloak. An authenticated user with low privileges can exploit this vulnerability by sending an oversized subject_token JSON Web Token (JWT) to the TokenEndpoint. When the token exceeds a 4000-character limit, it is silently dropped, causing the system to fall back to client credentials. This allows the user to gain the permissions of the client's service account, leading to privilege escalation.

CVSS: 8.8
EPSS: 0.32%
CISA KEV: Not listed
Published: 2026.05.27

PRIORITY ASSESSMENT

Review review

The CVSS severity warrants an early asset and exposure review.

Known exploitationNot established by KEV

Exploit probability0.32%

Technical severityCVSS 8.8

Vulnerability overview

Affected product and versions

Product: Red Hat Red Hat build of Keycloak 26.4, Red Hat build of Keycloak 26.4.13, Red Hat build of Keycloak 26.6
Affected versions: See the vendor advisory and NVD configuration data
Fixed versions: No verified fixed-version field is available yet

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide

1
Identify
Confirm that Red Hat Red Hat build of Keycloak 26.4, Red Hat build of Keycloak 26.4.13, Red Hat build of Keycloak 26.6 and an affected version are present.
2
Prioritize
Combine exploitation signals with asset exposure and business criticality.
3
Remediate
Follow the vendor advisory or supported update path and preserve rollback options.
4
Verify
Recheck the version, service health, access paths, and relevant logs.

Technical data

CVSS vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CWE: CWE-1284