Red Hat Keycloak CVE-2026-9793

Exploitation requires that the target Keycloak instance is configured to accept JWE-encrypted request objects on at least one OIDC client - this is not a default configuration and must be explicitly enabled per client in Keycloak's advanced settings. The attacker must have network access to the Keycloak OIDC authorization endpoint (standard HTTP/HTTPS); the CVSS vector PR:N indicates no client authentication credential is required to submit the malformed request object. Keycloak's public encryption key (needed to craft the JWE payload) must be obtainable, which is standard via the JWKS endpoint. Exploitation is further limited by the following factors: a properly configured redirect URI allowlist reduces the practical impact by restricting where the manipulated authorization flow can redirect; SSVC marks this as non-automatable, meaning bulk opportunistic scanning is not viable; and the attack is relevant primarily to FAPI-compliant or financial-sector deployments where encrypted request objects are mandated. Standard enterprise Keycloak deployments not using JWE request objects are not exploitable.

The CVSS 3.1 score of 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N) reflects a high integrity impact with low attack complexity and no authentication barrier, which correctly captures the worst-case scenario. However, real-world risk is substantially moderated by several signals: EPSS is 0.02% (4th percentile), indicating extremely low observed exploitation probability; SSVC classifies exploitation as 'none' and automatable as 'no', meaning this is not a spray-and-pray attack; and the technical impact is rated 'partial' rather than total. The vulnerability only materializes when JWE-encrypted request objects are accepted, a feature that typically requires explicit OIDC client configuration and is most prevalent in FAPI or financial-sector deployments. For standard Keycloak deployments not using encrypted request objects, exploitation is not possible. Multiple Red Hat errata (RHSA-2026:50846 through 50849) indicate patches are available, reducing dwell-time risk. Overall, this is a high-priority patch for FAPI and regulated-sector deployments but lower urgency for standard enterprise SSO installations.

An attacker targeting a Keycloak instance with JWE-encrypted request objects enabled constructs a JWE payload encrypting raw JSON (rather than a signed JWT) to Keycloak's public encryption key, which is typically obtainable from the JWKS endpoint. The attacker submits this JWE as the request parameter in an OIDC authorization request; Keycloak decrypts the payload but - due to the signature verification bypass - processes the raw JSON claims directly without enforcing the signature policy. This allows the attacker to inject crafted claims (e.g., elevated roles, modified redirect URIs beyond the allowlist, or altered client scopes) into the authorization flow, corrupting the integrity of the resulting OIDC token. No public proof-of-concept code has been identified at time of analysis.