soroban-fixed-point-math is a fixed-point math library for Soroban smart contacts. In versions 1.3.0 and 1.4.0, the mulDiv(x, y, z) function incorrectly handled cases where both the intermediate product $x * y$ and the divisor $z$ were negative. The logic assumed that if the intermediate product was negative, the final result must also be negative, neglecting the sign of $z$. This resulted in rounding being applied in the wrong direction for cases where both $x * y$ and $z$ were negative. The functions most at risk are fixed_div_floor and fixed_div_ceil, as they often use non-constant numbers as the divisor $z$ in mulDiv. This error is present in all signed FixedPoint and SorobanFixedPoint implementations, including i64, i128, and I256. Versions 1.3.1 and 1.4.1 contain a patch. No known workarounds for this issue are available.
Weakness
The product performs a calculation that generates incorrect or unintended results that are later used in security-critical decisions or resource management.
Potential Mitigations
- Use languages, libraries, or frameworks that make it easier to handle numbers without unexpected consequences.
- Examples include safe integer handling packages such as SafeInt (C++) or IntegerLib (C or C++).
- Use languages, libraries, or frameworks that make it easier to handle numbers without unexpected consequences.
- Examples include safe integer handling packages such as SafeInt (C++) or IntegerLib (C or C++).
Related Attack Patterns
References
- https://github.com/script3/soroban-fixed-point-math/commit/c9233f7094198a49ed66a4d75786a8a3755c936a
- https://github.com/script3/soroban-fixed-point-math/releases/tag/v1.3.1
- https://github.com/script3/soroban-fixed-point-math/releases/tag/v1.4.1
- https://github.com/script3/soroban-fixed-point-math/security/advisories/GHSA-x5m4-43jf-hh65