CVE-2026-9704

MEDIUM

Keycloak: keycloak: privilege escalation due to oversized subject_token jwt

Title source: cna
STIX 2.1

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.

References (4)

Core 4
Core References
Vendor Advisory vendor-advisory x_refsource_redhat
RHSA-2026:25097
https://access.redhat.com/errata/RHSA-2026:25097
Vendor Advisory vendor-advisory x_refsource_redhat
RHSA-2026:25098
https://access.redhat.com/errata/RHSA-2026:25098
Vdb Entry, X_Refsource_Redhat vdb-entry x_refsource_redhat
https://access.redhat.com/security/cve/CVE-2026-9704
Issue Tracking, X_Refsource_Redhat issue-tracking x_refsource_redhat
RHBZ#2481877
https://bugzilla.redhat.com/show_bug.cgi?id=2481877

Scores

CVSS v3 6.8
EPSS 0.0030
EPSS Percentile 21.4%
Attack Vector NETWORK
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N

CISA SSVC

Vulnrichment
Exploitation none
Automatable no
Technical Impact total

Details

CWE
CWE-1284
Status published
Products (5)
Red Hat/Red Hat Build of Keycloak
Red Hat/Red Hat build of Keycloak 26.6 26.6-6
Red Hat/Red Hat build of Keycloak 26.6 26.6.3-3
Red Hat/Red Hat build of Keycloak 26.6.3
redhat/build_of_keycloak
Published May 27, 2026
Tracked Since May 27, 2026