# ClampLib::mulDivDownInverse reverts on `target == type(uint256).max` before the overflow guard runs Low/Info · Blackthorn · Fixed-rate lending · 22nd May, 2026 Finding L-3 of the Tenor Morpho Migrations security review. - Protocol: https://www.tenor.finance/ - Report: /reports/tenor-markets - Source: https://github.com/tenor-labs/tenor-contracts/blob/main/audits/2026-06-Blackthorn-review.pdf --- ## Summary `mulDivDownInverse` computes `n = target + 1` before its overflow guard, so `target == type(uint256).max` reverts with arithmetic overflow instead of returning `type(uint256).max` as the guard's intent implies. ## Vulnerability Detail The [function](https://github.com/sherlock-audit/2026-05-tenor-markets-may-21st-2026/blob/main/tenor-morpho-v2-contracts-2/src/periphery/libraries/ClampLib.sol#L232-L238): ```solidity function mulDivDownInverse(uint256 target, uint256 den, uint256 num) internal pure returns (uint256) { uint256 n = target + 1; if (n == 0 || den > type(uint256).max / n) { return type(uint256).max; // overflow -> this constraint is not the bottleneck } return (n * den - 1) / num; } ``` With Solidity 0.8.x checked arithmetic, `target + 1` reverts when `target == type(uint256).max`. The guard immediately below is meant to handle the overflow case by returning `type(uint256).max`, but it never executes. `getOfferRemaining` reaches this function with `remainingAssets` derived from `offer.maxAssets`, which is a `uint256` controlled by the maker. A maker setting `offer.maxAssets = type(uint256).max` (or any value such that `remainingAssets` equals `type(uint256).max`) DoSes any helper that calls `getOfferRemaining` for that offer, including the router's clamp logic. ## Impact Callers reading offer state for a maker-controlled `offer.maxAssets == type(uint256).max` revert instead of receiving the documented "unbounded" sentinel, blocking offer reads and any clamp-based path that consumes them. ## Code Snippet https://github.com/sherlock-audit/2026-05-tenor-markets-may-21st-2026/blob/main/tenor-morpho-v2-contracts-2/src/periphery/libraries/ClampLib.sol#L233 ## Tool Used Manual Review ## Recommendation Short-circuit before the addition: ```solidity function mulDivDownInverse(uint256 target, uint256 den, uint256 num) internal pure returns (uint256) { if (target == type(uint256).max) return type(uint256).max; uint256 n = target + 1; if (den > type(uint256).max / n) { return type(uint256).max; } return (n * den - 1) / num; } ``` --- Related findings: - [Reentrancy guard can be implemented with a uint256 to save gas](https://0xsimao.com/findings/orange-reentrancy-guard-implemented-gas): Orange Bridge - [Index underflow is not protected against, although it has no impact as the pool with index type(uint256).max should not be registered](https://0xsimao.com/findings/nftperp-ii-index-underflow-impact-registered): Nftperp Matching Engine - [mul() and div() in NFTPMath are misleading due to scaling by 1e18 underneath](https://0xsimao.com/findings/nftperp-i-nftp-scaling-1e18-underneath): Nftperp Exchange - [`LenderCommitmentGroup_Smart` does not use `mulDiv` when converting between token and share amounts, possibly leading to DoS or loss of funds](https://0xsimao.com/findings/teller-finance-mul-div-converting-share): Teller Finance