Man-in-the-Middle (MitM) Affecting https-proxy-agent package, versions <2.2.3



    Attack Complexity High
    Scope Changed
    Confidentiality High

    Threat Intelligence

    Exploit Maturity Proof of concept

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  • published 2 Oct 2019
  • disclosed 25 Sep 2019
  • credit Kris Adler

Introduced: 25 Sep 2019

CVE NOT AVAILABLE CWE-300 Open this link in a new tab

How to fix?

Upgrade https-proxy-agent to version 2.2.3 or higher.


https-proxy-agent is a module that provides an http.Agent implementation that connects to a specified HTTP or HTTPS proxy server, and can be used with the built-in https module.

Affected versions of this package are vulnerable to Man-in-the-Middle (MitM). When targeting a HTTP proxy, https-proxy-agent opens a socket to the proxy, and sends the proxy server a CONNECT request. If the proxy server responds with something other than a HTTP response 200, https-proxy-agent incorrectly returns the socket without any TLS upgrade. This request data may contain basic auth credentials or other secrets, is sent over an unencrypted connection. A suitably positioned attacker could steal these secrets and impersonate the client.

PoC by Kris Adler

var url = require('url');
var https = require('https');
var HttpsProxyAgent = require('https-proxy-agent');

var proxyOpts = url.parse(';); var opts = url.parse(';); var agent = new HttpsProxyAgent(proxyOpts); opts.agent = agent; opts.auth = 'username:password'; https.get(opts);