CVE-2026-9704

HighCVSS 8.8/10Last modified Jun 26, 2026

Description

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.

Metrics

CVSS 3.1 8.8/10CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Weakness enumeration

CWE-1284

Affected software

No affected versions have been published.

Timeline

Published: May 27, 2026
Last modified: Jun 26, 2026
NVD status: Modified

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