js-yaml@1.0.0 vulnerabilities

YAML 1.2 parser and serializer

Direct Vulnerabilities

Known vulnerabilities in the js-yaml package. This does not include vulnerabilities belonging to this package’s dependencies.

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Vulnerability Vulnerable Version
  • H
Arbitrary Code Execution

js-yaml is a human-friendly data serialization language.

Affected versions of this package are vulnerable to Arbitrary Code Execution. When an object with an executable toString() property used as a map key, it will execute that function. This happens only for load(), which should not be used with untrusted data anyway. safeLoad() is not affected because it can't parse functions.

How to fix Arbitrary Code Execution?

Upgrade js-yaml to version 3.13.1 or higher.

<3.13.1
  • M
Denial of Service (DoS)

js-yaml is a human-friendly data serialization language.

Affected versions of this package are vulnerable to Denial of Service (DoS). It's possible to abuse aliases to create an exponential tree of nodes consisting of collections that each have multiple references. When such a tree is used as the key of a mapping it is then converted to a JS object, which is then parsed by JSON.stringify(), which causes the process to run out of memory creating the string.

How to fix Denial of Service (DoS)?

Upgrade js-yaml to version 1.5.0 or higher.

<1.5.0
  • M
Code Execution due to Deserialization

The JS-YAML module for Node.js contained a code execution vulnerability prior to version 2.0.5. The maintainers of JS-YAML have patched this vulnerability and, beginning in version 2.1.0, have provided a safeLoad method for parsing YAML. Developers that use this module should make sure they have upgraded and should strongly consider porting their code to use the new safeLoad method.

Source: Node Security Project

Details

The module allowed code execution due to a custom data-type that it defined and parsed called !!js/function. The way it would parse the data was to create a new Function object in JavaScript based on the input, which is equivalent to calling eval on the input:

function resolveJavascriptFunction(object /*, explicit*/) {
  /*jslint evil:true*/
  var func;

  try {
    func = new Function('return ' + object);
    return func();
  } catch (error) {
    return NIL;
  }
}

That meant the code snippet below, when run, would execute code instead of simply defining a function:

var yaml = require('js-yaml');

x = "test: !!js/function > \n  \
function f() { \n    \
console.log(1); \n  \
}();"

yaml.load(x);

How to fix Code Execution due to Deserialization?

Developers using the JS-YAML module should make sure that they are working with an up-to-date version and should strongly consider porting their code to use safeLoad in place of load, especially when accepting YAML derived from user input.

<2.0.5