Blunt Alabaster Kookaburra
Medium
The FullMath library, adapted for Teller's protocol from Uniswap V3, fails to handle overflows correctly under Solidity ≥0.8.0. This causes execution to revert during critical calculations when intermediate values exceed the 256-bit limit, disrupting the intended functionality of the library.
The original FullMath library in UniswapV3 was designed for Solidity <0.8.0, where overflows were not automatically checked.
https://github.com/Uniswap/v3-core/blob/main/contracts/libraries/FullMath.sol
But in Teller protocol, the FullMath library has been adapted from Uniswap V3 for use with Solidity ≥0.8.0.
https://github.com/sherlock-audit/2024-11-teller-finance-update/blob/0c8535728f97d37a4052d2a25909d28db886a422/teller-protocol-v2-audit-2024/packages/contracts/contracts/libraries/uniswap/FullMath.sol#L2
With Solidity ≥0.8.0, overflow checks are enforced, causing reversion in calculations that rely on the "phantom overflow" behavior of the original library.
This effectively means that when a phantom overflow (a multiplication and division where an intermediate value overflows 256 bits) occurs the execution will revert and the correct result won't be returned.
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Execution reverts during calculations requiring intermediate overflows
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Replace the current FullMath implementation with the 0.8 version in the Uniswap repository.