Uninitialized Memory Exposure Affecting tunnel-agent package, versions <0.6.0



    Attack Complexity High
    Confidentiality High

    Threat Intelligence

    Exploit Maturity Proof of concept

Do your applications use this vulnerable package?

In a few clicks we can analyze your entire application and see what components are vulnerable in your application, and suggest you quick fixes.

Test your applications
  • Snyk ID npm:tunnel-agent:20170305
  • published 5 Jul 2017
  • disclosed 4 Mar 2017
  • credit ChALkeR

Introduced: 4 Mar 2017

CVE NOT AVAILABLE CWE-201 Open this link in a new tab

How to fix?

Upgrade tunnel-agent to version 0.6.0 or higher. Note This is vulnerable only for Node <=4


tunnel-agent is HTTP proxy tunneling agent. Affected versions of the package are vulnerable to Uninitialized Memory Exposure.

A possible memory disclosure vulnerability exists when a value of type number is used to set the proxy.auth option of a request request and results in a possible uninitialized memory exposures in the request body.

This is a result of unobstructed use of the Buffer constructor, whose insecure default constructor increases the odds of memory leakage.


Constructing a Buffer class with integer N creates a Buffer of length N with raw (not "zero-ed") memory.

In the following example, the first call would allocate 100 bytes of memory, while the second example will allocate the memory needed for the string "100":

// uninitialized Buffer of length 100
x = new Buffer(100);
// initialized Buffer with value of '100'
x = new Buffer('100');

tunnel-agent's request construction uses the default Buffer constructor as-is, making it easy to append uninitialized memory to an existing list. If the value of the buffer list is exposed to users, it may expose raw server side memory, potentially holding secrets, private data and code. This is a similar vulnerability to the infamous Heartbleed flaw in OpenSSL.

Proof of concept by ChALkeR

  method: 'GET',
  uri: 'http://www.example.com',
  tunnel: true,
      protocol: 'http:',

You can read more about the insecure Buffer behavior on our blog.

Similar vulnerabilities were discovered in request, mongoose, ws and sequelize.