{"cve":"CVE-2026-53728","nvd":{"published":"2026-09-03T20:17:21.643","modified":"2026-09-09T21:09:13.080","status":"Deferred","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_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:L","score":7.1},"cwes":["CWE-345","CWE-601"],"references":["https://github.com/medplum/medplum/commit/7ae10035ddadde4dba7b18d3156553940465b3a1","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"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:52:03.409947763+00:00"},"epss":{"cve":"CVE-2026-53728","score":0.00198,"percentile":0.09641,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-m44r-7c5h-m6mj","url":"https://osv.dev/vulnerability/GHSA-m44r-7c5h-m6mj","summary":"Medplum: Improper Validation of Redirect URI in External Auth Callback allows Authorization Code Leakage","modified":"2026-08-17T13:55:59.945777Z","packages":[{"ecosystem":"npm","name":"@medplum/core","purl":"pkg:npm/%40medplum/core","ranges":["<5.1.6"],"fixed":["5.1.6"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}