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CVE-2026-53728 high CVSS 7.1

Vulnerability in @medplum/core (CVE-2026-53728)

Summary

Vulnerability in @medplum/core (CVE-2026-53728). Confidential information can be exposed externally. Exploitable via GET /auth/external. Mitigation: upgrade to 5.1.6 or later.

Original description

The description as published by the source.

Summary

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.

Technical Explanation

The vulnerable flow is exposed on the unauthenticated callback route GET /auth/external.

In externalCallbackHandler(), the server parses the external auth state and uses the decoded clientId and redirectUri after completing the IdP code exchange. If login succeeds and a client is found, the handler calls:

  • getClientRedirectUri(client, body.redirectUri, true)

The third argument explicitly enables partial matching. In getClientRedirectUri(), the function returns the attacker-supplied requestedUri whenever:

  • requestedUri.startsWith(uri)

As a result, any redirect URI beginning with a registered value is accepted. The returned URL is then passed into new URL(redirectUri)…

Source: GitHub Security Advisories (Global) NVD GitHub Advisory

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as CVE-2026-53728 has been found in @medplum/core.
Attackers can target a specific entry point like GET /auth/external over the network to misuse the product.
Confidential information can be exposed externally. CVSS score: 7.1/10.
What to do: upgrade @medplum/core to 5.1.6 or later.
If unsure, ask your IT team or search "@medplum/core CVE-2026-53728" on the vendor's site.

CVE-2026-53728 (@medplum/core) — CWE-345 / CVSS v3 7.1
Attack vector: remote (network-reachable) / unauthenticated
Attack surface: GET /auth/external / login / code / state
Patched: 5.1.6 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

A vulnerability (CWE-345) exists in @medplum/core. Attackers reach the vulnerable code path via GET /auth/external without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of @medplum/core. Attack surface: GET /auth/external / login / code / state.

🔥 Severity

Severity: High (CVSS 7.1/10). Confidential information can be exposed externally.

🔧 How to fix

Update to 5.1.6.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual GET /auth/external requests with malformed payloads or SQL meta-characters. Run grep -r '@medplum/core' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

  1. 1
    Identify exposure identify 
    grep -r '@medplum/core' . | grep -v node_modules

    リポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で @medplum/core を grep し、稼働しているサービス・バージョンを把握する。

  2. 2
    Hunt for indicators of compromise detect 
    grep 'GET /auth/external' /var/log/nginx/access.log | grep -E '(unusual_payload|sqli_pattern)'

    アクセスログで GET /auth/external への異常なリクエスト (不正な認証ヘッダ・SQLメタ文字)を過去 30〜90日分捜索。WAF/SIEM があれば該当パスのアラート発火履歴を確認。

  3. 3
    Apply patch patch 
    Upgrade @medplum/core to 5.1.6

    ステージング環境で 5.1.6 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスと、Step 2 で見つけた異常検知の続報チェックを含めること。

  4. 4
    Post-deployment verification verify 
    Replay attack against GET /auth/external on staging to confirm patch closes the vector

    パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番では Step 2 と同じログクエリでアラート再発が無いか継続監視。

Affected packages

npm @medplum/core
[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"5.1.6"}]}]

References

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