Log in Start free

Vulnerability · Published Sep 3, 2026 · Assigned by GitHub_M

CVE-2026-53728Medplum - Improper Validation of Redirect URI in External Auth Callback allows Authorization Code Leakage

High 7.1

In plain English

A high-severity open redirect in medplum from medplum. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 10% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)7.1High
Exploit odds (30 days)0.2%top 90.3% of all CVEs
Exploited in the wildNo reportsCISA SSVC: poc
Attack toolingNoneno public tooling known

Official 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.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
npm@medplum/core5.1.6GHSA-m44r-7c5h-m6mj

Affected products (as reported)

VendorProductVersions
medplum medplum < 5.1.6

Weakness: CWE-601, CWE-345 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:L

References