Denial of Service (DoS) Affecting pow_assent package, versions <0.4.4



    Attack Complexity Low
    Availability High

    Threat Intelligence

    EPSS 0.04% (6th percentile)
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5.5 medium

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  • Snyk ID SNYK-HEX-POWASSENT-1086577
  • published 18 Mar 2021
  • disclosed 25 Nov 2019
  • credit Unknown

How to fix?

Upgrade pow_assent to version 0.4.4 or higher.


Affected versions of this package are vulnerable to Denial of Service (DoS) via the use of String.to_atom/1 in PowAssent. In PowAssent.Phoenix.AuthorizationController a value is fetched from the user provided params, and String.to_atom/1 is used to convert the binary value to an atom so it can be used to fetch the provider configuration value. This is unsafe as it is user provided data, and can be used to fill up the whole atom table of ~1M which will cause the app to crash.

A workaround is to use a plug to validate conn.params["provider"] before it reaches the PowAssent.Phoenix.AuthorizationController.


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