js-yaml@2.0.4

Vulnerabilities 2 via 2 paths
Dependencies 3
Source npm
Package js-yaml

Find, fix and prevent vulnerabilities in your code.

Severity
  • 1
  • 1
Status
  • 2
  • 0
  • 0
high severity

Arbitrary Code Execution

  • Vulnerable module: js-yaml
  • Introduced through: js-yaml@2.0.4

Detailed paths

  • Introduced through: js-yaml@2.0.4
    Remediation: Upgrade to js-yaml@3.13.1.

Overview

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.

Remediation

Upgrade js-yaml to version 3.13.1 or higher.

References

medium severity

Code Execution due to Deserialization

  • Vulnerable module: js-yaml
  • Introduced through: js-yaml@2.0.4

Detailed paths

  • Introduced through: js-yaml@2.0.4
    Remediation: Upgrade to js-yaml@2.0.5.

Overview

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);

Remediation

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.

References