Vulnerability in Red Hat Build Of Keycloak
CVE-2026-9704
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 6.8 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N.
EPSS exploit prediction
EPSS: 0.006 (45.9th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 46th percentile — 45.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.006 · change: +0.003
Affected products
- Red Hat Build Of Keycloak
- Red Hat Build Of Keycloak 26.4 — versions 26.4.13-1, 26.4-19
- Red Hat Build Of Keycloak 26.4.13
- Red Hat Build Of Keycloak 26.6 — versions 26.6-8, 26.6-6, 26.6.3-3
- Red Hat Build Of Keycloak 26.6.3
- Red Hat Build Of Keycloak 26.6.4
- Red Hat Build Of Keycloak
Weakness classification (CWE)
References
- access.redhat.com/security/cve/CVE-2026-9704 (Mitigation, vdb-entry, Vendor Advisory)
- bugzilla.redhat.com/show_bug.cgi (issue-tracking, Issue Tracking, Vendor Advisory)
- access.redhat.com/errata/RHSA-2026:25098 (vendor-advisory)
- access.redhat.com/errata/RHSA-2026:25097 (vendor-advisory)
- access.redhat.com/errata/RHSA-2026:30049 (vendor-advisory)
- access.redhat.com/errata/RHSA-2026:30050 (vendor-advisory)
Frequently asked questions
- What is CVE-2026-9704?
- CVE-2026-9704 is a medium-severity vulnerability in Red Hat Build Of Keycloak, classified under Improper Validation of Specified Quantity in Input. CVSS score: 6.8/10. Published 2026-05-27.
- How severe is CVE-2026-9704?
- Medium severity. CVSS v3 base score is 6.8 out of 10.