CVE-2026-24783

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.

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.

### Impact #### Incorrect rounding direction for signed mul and div operations 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`. #### Negative Overflow in `i64` The `mulDiv(x, y, z)` function for `i64` used the `i128` type to handle "phantom overflows". These are overflows that occur intermediately during a calculation, like when computing the intermediate product $x * y$. When the final result of `mulDiv` was computed in `i128`, it was scaled back down to `i64` before returning. While the code verified that the result did not exceed `i64::MAX`, it did not check against `i64::MIN`. This caused negative results smaller than `i64:MIN` to wrap around to a large positive number instead of being caught as an overflow. This error only exists for the `FixedPoint` implementation of `i64`. ### Patches * v1.3.0 users should upgrade to patch v1.3.1 * v1.4.0 users should upgrade to patch v1.4.1 All versions `>=v1.4.1` contain the patch. ### Workarounds There are no known workarounds. Upgrade to the patched version. ### Credits soroban-fixed-point-math would like to thank the team at [Certora](https://www.certora.com/) for discovering and reporting the issue.

### Impact #### Incorrect rounding direction for signed mul and div operations 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`. #### Negative Overflow in `i64` The `mulDiv(x, y, z)` function for `i64` used the `i128` type to handle "phantom overflows". These are overflows that occur intermediately during a calculation, like when computing the intermediate product $x * y$. When the final result of `mulDiv` was computed in `i128`, it was scaled back down to `i64` before returning. While the code verified that the result did not exceed `i64::MAX`, it did not check against `i64::MIN`. This caused negative results smaller than `i64:MIN` to wrap around to a large positive number instead of being caught as an overflow. This error only exists for the `FixedPoint` implementation of `i64`. ### Patches * v1.3.0 users should upgrade to patch v1.3.1 * v1.4.0 users should upgrade to patch v1.4.1 All versions `>=v1.4.1` contain the patch. ### Workarounds There are no known workarounds. Upgrade to the patched version. ### Credits soroban-fixed-point-math would like to thank the team at [Certora](https://www.certora.com/) for discovering and reporting the issue.

soroban-fixed-point-math es una librería de matemáticas de punto fijo para contratos inteligentes de Soroban. En las versiones 1.3.0 y 1.4.0, la función 'mulDiv(x, y, z)' manejó incorrectamente los casos en que tanto el producto intermedio $x * y$ como el divisor $z$ eran negativos. La lógica asumía que si el producto intermedio era negativo, el resultado final también debía ser negativo, ignorando el signo de $z$. Esto resultó en que el redondeo se aplicara en la dirección incorrecta para los casos en que tanto $x * y$ como $z$ eran negativos. Las funciones con mayor riesgo son 'fixed_div_floor' y 'fixed_div_ceil', ya que a menudo usan números no constantes como el divisor $z$ en 'mulDiv'. Este error está presente en todas las implementaciones firmadas de 'FixedPoint' y 'SorobanFixedPoint', incluyendo 'i64', 'i128' e 'I256'. Las versiones 1.3.1 y 1.4.1 contienen un parche. No se conocen soluciones alternativas disponibles para este problema.