CVE-2026-9704

What it is

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.

At a glance

Exploitability

Can be exploited over the network with a low-privilege account. High risk of data exposure, data tampering.

Exploit odds

0.3% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2026-05-27 14:17 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-26 08:16 UTC Last updatedMost recent change to the record

Details

Published

2026-05-27 14:17 UTC

Last modified

2026-06-26 08:16 UTC

Exploit probability

0.3% · EPSS, next 30 days

Weakness

CWE-1284

Record status

Modified

Affected

• Redhat Build Of Keycloak

Attack profile CVSS 3.1 · 6.8

Attack vector

Network

Complexity

High

Privileges needed

Low

User interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

None