CVE-2026-9704

[CVE catalog]

Severity

Medium · CVSS 6.8CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N

Published

May 27, 2026, 12:45:59 PM UTC

Source

[NVD] · [CVE record]

EPSS

0.32% · Oct 27, 2026

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. keycloak: Keycloak: Privilege escalation due to oversized subject_token JWT This Moderate flaw in Keycloak allows an authenticated, low-privileged user to escalate privileges. By submitting an oversized `subject_token` JWT to the TokenEndpoint, the system defaults to client credentials, granting the attacker the client's service account permissions. This bypass occurs when the token exceeds a 4000-character limit, leading to an unintended privilege gain. The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.