FUXA: Unauthenticated SSRF via Socket.IO DEVICE_WEBAPI_REQUEST and DEVICE_PROPERTY with response reading

Summary

An unauthenticated attacker (Alice) connects to FUXA's Socket.IO endpoint and emits a device-webapi-request event whose property.address field names an arbitrary URL. FUXA's DEVICE_WEBAPI_REQUEST handler at server/runtime/index.js:296 calls axios.get(address) server-side and broadcasts the full response body back on the same event via io.emit. The companion handler DEVICE_PROPERTY at server/runtime/index.js:153 has the same miss against OPC UA and ODBC endpoints. Both handlers skip the isSocketWriteAuthorized() check that the other write-capable events (DEVICE_VALUES at line 182, DEVICE_ENABLE at line 358) call. Alice reads cloud instance metadata, scans internal services, and connects to any OPC UA server or ODBC database the FUXA host can reach, then receives the results.

Details

Vulnerable handlers: server/runtime/index.js:153-171, 296-316:

socket.on(Events.IoEventTypes.DEVICE_PROPERTY, (message) => {
    try {
        if (message && message.endpoint && message.type) {
            devices.getSupportedProperty(message.endpoint, message.type).then(result => {
                message.result = result;
                io.emit(Events.IoEventTypes.DEVICE_PROPERTY, message);
            })
            // ...
        }
    }
    // ...
});

socket.on(Events.IoEventTypes.DEVICE_WEBAPI_REQUEST, (message) => {
    try {
        if (message && message.property) {
            devices.getRequestResult(message.property).then(result => {
                message.result = result;
                io.emit(Events.IoEventTypes.DEVICE_WEBAPI_REQUEST, message);
            })
            // ...
        }
    }
    // ...
});

Sink: server/runtime/devices/httprequest/index.js:471 for the webapi path:

if (property.method === 'GET') {
    axios.get(property.address).then(res => {
        resolve(res.data);
    // ...

Alice fully controls property.address, and io.emit echoes the response body back on the same event. For the ODBC variant, server/runtime/devices/odbc/index.js builds the connection string from endpoint.address plus endpoint.uid and endpoint.pwd, so Alice supplies credentials and targets any reachable ODBC server.

Contrast: server/runtime/index.js:182 (the DEVICE_VALUES write handler) gates the exact same kind of action behind isSocketWriteAuthorized(socket). The two handlers above skip that check.

Reachability: neither handler performs any authorization check, so both modes reach the sinks. secureEnabled=true does not close the gap because the Socket.IO connect block at server/runtime/index.js:114-120 auto-issues a guest token to any client that connects without one, and the handlers run regardless of socket.isAuthenticated. This is the same pattern GHSA-vwcg-c828-9822's note warned about: enabling authentication does not mitigate the missing check here.

Impact

Alice uses FUXA as a read-SSRF oracle against any HTTP(S) service the FUXA host can reach, with the response body delivered back to her Socket.IO session. On cloud-hosted SCADA deployments this exfiltrates IAM credentials from the instance metadata service. On OT networks it reaches internal OPC UA servers, ODBC databases, and administrative consoles that have no other external exposure. The ODBC variant accepts attacker-supplied credentials, so Alice authenticates to any ODBC server that trusts connections from the FUXA host. The attack works against secureEnabled=true deployments as well as the default; no operator interaction required.

CVSS 3.1: AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N (High, 8.2). CWE-918.

Recommended Fix

Add the existing isSocketWriteAuthorized(socket) check at the top of both handlers, matching the pattern used by DEVICE_VALUES and DEVICE_ENABLE. Also switch io.emit to socket.emit so the response scopes to the requesting socket instead of broadcasting to every connected client. For defense in depth, validate property.address against an allowlist of schemes and reject private, loopback, and link-local address ranges before calling axios.get or the device connect paths.

socket.on(Events.IoEventTypes.DEVICE_WEBAPI_REQUEST, (message) => {
    try {
        if (!isSocketWriteAuthorized(socket)) {
            logger.warn(`${Events.IoEventTypes.DEVICE_WEBAPI_REQUEST}: unauthorized request from ${socket.userId || 'guest'}`);
            return;
        }
        if (message && message.property) {
            // ... validate property.address against allowlist ...
            devices.getRequestResult(message.property).then(result => {
                message.result = result;
                socket.emit(Events.IoEventTypes.DEVICE_WEBAPI_REQUEST, message);
            })
            // ...
        }
    }
    // ...
});

Apply the same three changes (auth check, socket.emit, address validation) to DEVICE_PROPERTY.

A fix is available at https://github.com/frangoteam/FUXA/releases/tag/v1.3.2.

Found by aisafe.io