Denial of Service (DoS) Affecting eth-abi package, versions [,4.2.0)



    Attack Complexity Low

    Threat Intelligence

    Exploit Maturity Proof of concept

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  • Snyk ID SNYK-PYTHON-ETHABI-6085292
  • published 26 Nov 2023
  • disclosed 24 Nov 2023
  • credit Max Ammann

Introduced: 24 Nov 2023

CVE NOT AVAILABLE CWE-400 Open this link in a new tab

How to fix?

Upgrade eth-abi to version 4.2.0 or higher.


eth-abi is an eth_abi: Python utilities for working with Ethereum ABI definitions, especially encoding and decoding

Affected versions of this package are vulnerable to Denial of Service (DoS) when parsing zero-sized-types (ZST). Although allowed by the ABI specification, excessive memory can be allocated when processing malicious ZST tuples.


This vulnerability can be mitigated by disallowing the parsing of ZST.


  1. Define a payload of 0x0000000000000000000000000000000000000000000000000000000000000020 00000000000000000000000000000000000000000000000000000000FFFFFFFF as either a ()[] or a uint32[0][].

  2. Decode the payload using decode(), e.g.

from eth_abi import decode
data = bytearray.fromhex(payload)
decode(['()[]'], data)


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