Denial of Service (DoS) Affecting io.netty:netty-handler package, versions [4.0.0.Alpha1, 4.0.37.Final) [4.1.0.Beta1, 4.1.1.Final)



    Attack Complexity Low
    Availability High

    Threat Intelligence

    EPSS 1.66% (86th percentile)
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7.5 high
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Red Hat
3.7 low

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  • published 7 Jun 2016
  • disclosed 7 Jun 2016
  • credit Unknown

How to fix?

Upgrade io.netty:netty-handler 4.0.37.Final, 4.1.1.Final or higher.


io.netty:netty-handler Affected versions of this package are vulnerable to infinite loop Denial of Service (DoS) attacks via a flaw in Netty's OpenSslEngine handling of renegotiation.

Note: Netty is only vulnerable if renegotiation is enabled (It is a default setting).


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