How 1,000 Wei Can Drain Protocol Fees: A Deep Dive into CoW Protocol Rounding Errors

During my recent security research into the CoW Protocol (Gnosis Protocol v2), I focused on how the protocol handles fractional settlements. While the protocol is architecturally sound, a classic smart contract pitfall—precision loss—can lead to cumulative fee leakage. In this post, I’ll show how a malicious solver can exploit integer division in GPv2Settlement to execute trades with zero protocol fees. The Vulnerability: Death by a Thousand Cuts The core of the issue lies in how fees are calcul