CVE-2026-9704 — MEDIUM (6.8)

Vulnerability 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.

CVSS Score

6.8

MEDIUM

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

Attack Vector

NETWORK

Attack Complexity

HIGH

Privileges Required

LOW

User Interaction

NONE

Scope

UNCHANGED

Confidentiality

HIGH

Integrity

HIGH

Availability

NONE

Affected Products

Vendor	Product	Versions
Redhat	Build Of Keycloak	-

Related Weaknesses (CWE)

CWE-1284

References

https://access.redhat.com/errata/RHSA-2026:25097
https://access.redhat.com/errata/RHSA-2026:25098
https://access.redhat.com/errata/RHSA-2026:30049
https://access.redhat.com/errata/RHSA-2026:30050
https://access.redhat.com/security/cve/CVE-2026-9704MitigationVendor Advisory
https://bugzilla.redhat.com/show_bug.cgi?id=2481877Issue TrackingVendor Advisory

FAQ

What is CVE-2026-9704?

CVE-2026-9704 is a vulnerability with a CVSS score of 6.8 (MEDIUM). 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 e...

How severe is CVE-2026-9704?

CVE-2026-9704 has been rated MEDIUM with a CVSS base score of 6.8/10. Review the CVSS metrics above for detailed severity breakdown.

Is there a patch for CVE-2026-9704?

Check the references section above for vendor advisories and patch information. Affected products include: Redhat Build Of Keycloak.