Vulnerability Description
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.
CVSS Score
HIGH
Related Weaknesses (CWE)
References
- https://github.com/medplum/medplum/commit/7ae10035ddadde4dba7b18d3156553940465b3
- https://github.com/medplum/medplum/pull/8749
- https://github.com/medplum/medplum/releases/tag/v5.1.6
- https://github.com/medplum/medplum/security/advisories/GHSA-m44r-7c5h-m6mj
- https://github.com/medplum/medplum/security/advisories/GHSA-m44r-7c5h-m6mj
FAQ
What is CVE-2026-53728?
CVE-2026-53728 is a vulnerability with a CVSS score of 7.1 (HIGH). 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 ...
How severe is CVE-2026-53728?
CVE-2026-53728 has been rated HIGH with a CVSS base score of 7.1/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-53728?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.