---
title: "What is the most common vulnerability in ZK systems?"
description: "Underconstrained circuits. The great majority of exploitable findings in production ZK code are not breaks of the cryptography but circuits that accept…"
type: "question"
url: "https://zkpick.com/faq/what-is-the-most-common-vulnerability-in-zk-systems/"
section: "03 Auditing a ZK protocol"
authors:
  - "MarketComp"
publisher: "MarketComp"
version: "1.3"
updated: "2026-09-12"
license: "CC-BY-4.0"
json: "https://zkpick.com/data/faq/what-is-the-most-common-vulnerability-in-zk-systems.json"
---

*By MarketComp. Updated 2026-09-12. Version 1.3. CC BY 4.0.*

# What is the most common vulnerability in ZK systems?

Underconstrained circuits. The great majority of exploitable findings in production ZK code are not breaks of the cryptography but circuits that accept witnesses which do not correspond to a correct execution — a missing range check, an unconstrained intermediate signal, an unchecked division, an unenforced boolean. The proof is valid; it simply proves a weaker statement than the designers intended. See Section 03.