Code Execution due to Deserialization Affecting js-yaml package, versions <2.0.5
Threat Intelligence
Snyk has a published code exploit for this vulnerability.
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDnpm:js-yaml:20130623
- published23 Jun 2013
- disclosed23 Jun 2013
- creditNeal Poole
Introduced: 23 Jun 2013
CVE-2013-4660 (opens in a new tab)How to fix?
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.
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);