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.
Affected products
redhat: build of keycloak
References6
- access.redhat.com/security/cve/CVE-2026-9704 MitigationVendor Advisory
- bugzilla.redhat.com/show_bug.cgi?id=2481877 Issue TrackingVendor Advisory
- access.redhat.com/errata/RHSA-2026:25097
- access.redhat.com/errata/RHSA-2026:25098
- access.redhat.com/errata/RHSA-2026:30049
- access.redhat.com/errata/RHSA-2026:30050
Metrics
- CVSS 3.1
-
8.8
HIGH
Score source: NVD
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H - EPSS — exploit probability
- 0% percentile: 25 · as of 14 November 2026
- CWE
- CWE-1284
Could this be exploited in your environment?
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