CVE-2026-53728
HighCVSS 7.1Summary
Medplum prior to version 5.1.6 has a vulnerability in the external identity provider callback at GET /auth/external that accepts attacker-controlled redirect URIs that only need to start with a registered client redirect URI. After a successful external IdP login, the server appends Medplum login and code values to that attacker-supplied URL and issues a redirect. Because the external login request state is serialized as raw JSON and later trusted, an attacker who can tamper with state.redirectUri can cause Medplum to redirect authorization artifacts to an attacker-controlled endpoint, leading to a cross-origin authorization code leak. This issue has been patched in version 5.1.6.
Risk Assessment
An attacker could intercept authorization codes and login tokens, potentially leading to unauthorized access to user accounts and sensitive medical data.
Recommendation
Immediately upgrade Medplum to version 5.1.6 or later and review client redirect URI configurations.
Other vulnerabilities in Medplum
See all- CVE-2026-44506High
Medplum versions 4.1.10 through 5.1.6 have a vulnerability in the /oauth2/register endpoint that could return the client_secret of preconfigured OAuth clients defined via the defaultOAuthClients server configuration when a matching redirect_uri was provided. This issue has been patched in version 5.1.7.
- CVE-2026-49120High
Medplum before version 5.1.14 has an SSRF vulnerability in the subscription worker, allowing authenticated users to perform unauthorized network requests by creating FHIR Subscription resources with arbitrary endpoint URLs. Attackers can point subscriptions at internal addresses like cloud metadata services, databases, or container orchestration endpoints to exfiltrate IAM credentials and patient health records.
Original NVD description (English source)
Medplum is a developer platform that enables development of healthcare apps. Prior to version 5.1.6, the external identity provider callback at GET /auth/external accepts attacker-controlled redirect URIs that only need to start with a registered client redirect URI, rather than matching exactly. After a successful external IdP login, the server appends Medplum login and code values to that attacker-supplied URL and issues a redirect. Because the external login request state is serialized as raw JSON and later trusted by the callback, an attacker who can tamper with state.redirectUri can cause Medplum to redirect authorization artifacts to an attacker-controlled endpoint. When the registered redirect URI is a bare origin or another prefix that can be extended into a different hostname, this becomes a cross-origin authorization code leak. This issue has been patched in version 5.1.6.