medium6.8
CVE-2026-9704
Keycloak Vulnerable to Improper Validation of Specified Quantity in Input
Impact
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.
Affected packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| maven | org.keycloak:keycloak-server-spi-private | < 26.6.3 | 26.6.3 |
| maven | org.keycloak:keycloak-services | < 26.6.3 | 26.6.3 |
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| Redhat | Build Of Keycloak | All versions |
Weakness classification
References
- NVD record
- CVE.org record
- GitHub advisory
- https://github.com/advisories/GHSA-rr5q-3xwr-f323
- https://nvd.nist.gov/vuln/detail/CVE-2026-9704
- https://access.redhat.com/security/cve/CVE-2026-9704
- https://bugzilla.redhat.com/show_bug.cgi?id=2481877
- https://access.redhat.com/errata/RHSA-2026:25098
- https://access.redhat.com/errata/RHSA-2026:25097
- https://access.redhat.com/errata/RHSA-2026:30049
- https://access.redhat.com/errata/RHSA-2026:30050
- https://github.com/keycloak/keycloak/issues/49435
- https://github.com/keycloak/keycloak/pull/49472
- https://github.com/keycloak/keycloak/commit/f1e5b7776c42938d0782fd5846346b8f75c815e6