CVE-2026-9704
Keycloak Vulnerable to Improper Validation of Specified Quantity in Input
6.8
MEDIUM
CVSS 3.1
EPSS 0.32%
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.
How to fix CVE-2026-9704
To remediate CVE-2026-9704, upgrade the affected package to a fixed version below.
- —upgrade to 26.6.3 or later
- —upgrade to 26.6.3 or later
Is CVE-2026-9704 being exploited?
Low — EPSS is 0.3%, meaning exploitation activity has not been observed at scale.
Affected packages (2)
- from 0, < 26.6.3
- from 0, < 26.6.3
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 3.1 | MEDIUM6.8 | CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N |