Prototype Override Protection Bypass Affecting qs package, versions <6.0.4>=6.1.0 <6.1.2>=6.2.0 <6.2.3>=6.3.0 <6.3.2
Threat Intelligence
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:qs:20170213
- published1 Mar 2017
- disclosed13 Feb 2017
- creditSnyk Security Research Team
Introduced: 13 Feb 2017
CVE-2017-1000048 (opens in a new tab)How to fix?
Upgrade qs to version 6.0.4, 6.1.2, 6.2.3, 6.3.2 or higher.
Overview
qs is a querystring parser that supports nesting and arrays, with a depth limit.
Affected versions of this package are vulnerable to Prototype Override Protection Bypass. By default qs protects against attacks that attempt to overwrite an object's existing prototype properties, such as toString(), hasOwnProperty(),etc.
From qs documentation:
By default parameters that would overwrite properties on the object prototype are ignored, if you wish to keep the data from those fields either use plainObjects as mentioned above, or set allowPrototypes to true which will allow user input to overwrite those properties. WARNING It is generally a bad idea to enable this option as it can cause problems when attempting to use the properties that have been overwritten. Always be careful with this option.
Overwriting these properties can impact application logic, potentially allowing attackers to work around security controls, modify data, make the application unstable and more.
In versions of the package affected by this vulnerability, it is possible to circumvent this protection and overwrite prototype properties and functions by prefixing the name of the parameter with [ or ]. e.g. qs.parse("]=toString") will return {toString = true}, as a result, calling toString() on the object will throw an exception.
Example:
qs.parse('toString=foo', { allowPrototypes: false }) // {}
qs.parse("]=toString", { allowPrototypes: false }) // {toString = true} <== prototype overwritten
For more information, you can check out our blog.
Disclosure Timeline
- February 13th, 2017 - Reported the issue to package owner.
- February 13th, 2017 - Issue acknowledged by package owner.
- February 16th, 2017 - Partial fix released in versions
6.0.3,6.1.1,6.2.2,6.3.1. - March 6th, 2017 - Final fix released in versions
6.4.0,6.3.2,6.2.3,6.1.2and6.0.4