CVE-2026-9704

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.

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Produits concernés

• Red Hat build of Keycloak 26.4
• Red Hat build of Keycloak 26.4.13
• Red Hat build of Keycloak 26.6
• Red Hat build of Keycloak 26.6.3
• Redhat build of keycloak

Scores CVSS

Faiblesses (CWE)

• CWE-1284

Références

• https://access.redhat.com/errata/RHSA-2026:25097
• https://access.redhat.com/errata/RHSA-2026:25098
• https://access.redhat.com/errata/RHSA-2026:30049
• https://access.redhat.com/errata/RHSA-2026:30050
• https://access.redhat.com/security/cve/CVE-2026-9704 MitigationVendor Advisory
• https://bugzilla.redhat.com/show_bug.cgi?id=2481877 Issue TrackingVendor Advisory

Ailleurs

• NVD
• CVE.org
• CIRCL Vulnerability-Lookup
• CERT-FR
• GitHub Advisories