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CVE-2026-9704

Keycloak: keycloak: privilege escalation due to oversized subject_token jwt

Published: May 27, 2026Updated: May 27, 2026 Sources: CVE List NVD
NVD MITRE
6.8CVSS
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 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.

EPSS Score
N/A
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
Workaround Only

CVSS Vector Breakdown

AV:NAC:HPR:LUI:NS:UC:HI:HA:N
Exploitability
AV:NAttack Vector
Network
AC:HAttack Complexity
High
PR:LPrivileges Required
Low
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:HConfidentiality
High
I:HIntegrity
High
A:NAvailability
None

Weaknesses

CWE-1284

Affected Products

Red Hat Build of Keycloak
Red Hat

Exploitability

Workaround Available

References

https://access.redhat.com/security/cve/CVE-2026-9704
access.redhat.com
https://bugzilla.redhat.com/show_bug.cgi?id=2481877
bugzilla.redhat.com

Timeline

Published
May 27, 2026
Last Updated
May 27, 2026

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