57832 sc insight cap logic error in alchemistallocator

Submitted on Oct 29th 2025 at 05:52:35 UTC by @rbd3 for Audit Comp | Alchemix V3

• Report ID: #57832

• Report Type: Smart Contract

• Report severity: Insight

• Target: https://github.com/alchemix-finance/v3-poc/blob/immunefi_audit/src/AlchemistAllocator.sol

• Impacts:

Description

Brief/Intro

Unit mismatch error in the allocation and deallocation caps calculation compares asset units with BPS units directly without conversion, causing mathematically meaningless comparisons and severe artificial restrictions on fund withdrawals.

Vulnerability Details

// Current buggy code in AlchemistAllocator.sol:
uint256 absoluteCap = vault.absoluteCap(id);  // Returns: Asset units (wei)
uint256 relativeCap = vault.relativeCap(id);  // Returns: BPS units (WAD)
uint256 adjusted = absoluteCap < relativeCap ? absoluteCap : relativeCap;  // INCORRECT

The deallocate function in AlchemistAllocator incorrectly compares values in different units without conversion.

absoluteCap(id) → Asset units (e.g., 2000000000000000000 = 2 ETH in wei)

relativeCap(id) → BPS units (e.g., 500000000000000000 = 0.5e18 = 50%)

Impact Details

Comparing these directly is mathematically meaningless () and creates severe artificial restrictions, like asking "Is 2 kilometers less than 50 percent?"

References

https://github.com/alchemix-finance/v3-poc/blob/a192ab313c81ba3ab621d9ca1ee000110fbdd1e9/src/AlchemistAllocator.sol#L29-L44

https://github.com/alchemix-finance/v3-poc/blob/a192ab313c81ba3ab621d9ca1ee000110fbdd1e9/src/AlchemistAllocator.sol#L51-L66

Proof of Concept

Proof of Concept

In the actual code, cap isn't enforced. But if it is, this create a critical or high issue in MYT allocation and deallocation.