Denial of Service (DoS) Affecting qs package, versions <1.0.0



    Attack Complexity Low
    Availability High

    Threat Intelligence

    EPSS 5.96% (94th percentile)
Expand this section
5.3 medium
Expand this section
Red Hat
4.3 medium

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  • Snyk ID npm:qs:20140806
  • published 6 Aug 2014
  • disclosed 6 Aug 2014
  • credit Dustin Shiver

How to fix?

Upgrade qs to version 1.0.0 or higher.


qs is a querystring parser that supports nesting and arrays, with a depth limit.

Affected versions of this package are vulnerable to Denial of Service (DoS). During parsing, the qs module may create a sparse area (an array where no elements are filled), and grow that array to the necessary size based on the indices used on it. An attacker can specify a high index value in a query string, thus making the server allocate a respectively big array. Truly large values can cause the server to run out of memory and cause it to crash - thus enabling a Denial-of-Service attack.


Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its intended and legitimate users.

Unlike other vulnerabilities, DoS attacks usually do not aim at breaching security. Rather, they are focused on making websites and services unavailable to genuine users resulting in downtime.

One popular Denial of Service vulnerability is DDoS (a Distributed Denial of Service), an attack that attempts to clog network pipes to the system by generating a large volume of traffic from many machines.

When it comes to open source libraries, DoS vulnerabilities allow attackers to trigger such a crash or crippling of the service by using a flaw either in the application code or from the use of open source libraries.

Two common types of DoS vulnerabilities:

  • High CPU/Memory Consumption- An attacker sending crafted requests that could cause the system to take a disproportionate amount of time to process. For example, commons-fileupload:commons-fileupload.

  • Crash - An attacker sending crafted requests that could cause the system to crash. For Example, npm ws package