Denial of Service (DoS) Affecting org.apache.struts:struts2-core package, versions [2.3.7,2.3.34) [2.5,2.5.13)



    Attack Complexity Low
    Availability High

    Threat Intelligence

    EPSS 4.69% (92nd percentile)
Expand this section
7.5 high

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  • published 12 Sep 2017
  • disclosed 23 Aug 2017
  • credit Adam Cazzolla, Jonathan Bullock

How to fix?

Upgrade org.apache.struts:struts2-core to version 2.3.34, 2.5.13 or higher.


Apache Struts2 is a popular open-source framework for developing web applications in the Java programming language.

Affected versions of this package are vulnerable to Regular Expression Denial of Service (ReDoS) attacks. This is due to an incomplete fix for CVE-2017-7672. If an application allows enter an URL in a form field and built-in URLValidator is used, it is possible to prepare a special URL which will be used to overload server process when performing validation of the URL.


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