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 breakdown
CVSS 3.1
Attack Vector
Network
Attack Complexity
High
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None
Affected products
References
- VENDOR_ADVISORYhttps://access.redhat.com/errata/RHSA-2026:25097
- VENDOR_ADVISORYhttps://access.redhat.com/errata/RHSA-2026:25098
- VENDOR_ADVISORYhttps://access.redhat.com/errata/RHSA-2026:30049
- VENDOR_ADVISORYhttps://access.redhat.com/errata/RHSA-2026:30050
- VENDOR_ADVISORYhttps://access.redhat.com/security/cve/CVE-2026-9704
- MISChttps://bugzilla.redhat.com/show_bug.cgi?id=2481877
Updated 8m ago · 8 sources