Denial of Service (DoS) Affecting io.netty:netty-handler package, versions [,4.1.94.Final)

io.netty:netty-handler is a library that provides an asynchronous event-driven network application framework and tools for rapid development of maintainable high performance and high scalability protocol servers and clients. In other words, Netty is a NIO client server framework which enables quick and easy development of network applications such as protocol servers and clients. It greatly simplifies and streamlines network programming such as TCP and UDP socket server.

Affected versions of this package are vulnerable to Denial of Service (DoS) such that if the user has no idle timeout handler configured it might be possible for a remote peer to send a client hello packet which leads the server to buffer up to 16MB of data per connection.

The SniHandler class is a handler that waits for the TLS handshake to configure a SslHandler according to the indicated server name by the ClientHello record. For this matter it allocates a ByteBuf using the value defined in the ClientHello record.

Note:

An attacker can craft a packet that makes the SslClientHelloHandler to:

1. Allocate a 16MB ByteBuf.

2. Not fail decode method in buffer.

3. Get out of the loop without an exception.

The combination of this without the use of a timeout makes it easy to connect to a TCP server and allocate 16MB of heap memory per connection.

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

• GitHub Commit