HSEC-2026-0012

Dashboard / Vulnerabilities / HSEC-2026-0012

HSEC-2026-0012

Summary: Out-of-bounds read in Eq and Ord on numbers with extreme exponents

Details: # Out-of-bounds read in Eq and Ord on numbers with extreme exponents `scientific-0.3.9.0` reimplemented `Eq` and `Ord` without normalising their arguments. The new implementation short-circuits on `integerLog10' c + e` computed in `Int`, which overflows when the base-10 exponent is close to `maxBound :: Int`. The overflowed comparison then falls through to `magnitude (e1 - e2)`, where the exponent difference overflows to a negative `Int` as well. `magnitude` indexed its cached power-of-ten array without a bounds check, so the negative index performed an out-of-bounds read and the process died with `SIGSEGV`. With `scientific-0.3.9.0` (GHC 9.10.3, x86_64-linux), as reported in [basvandijk/scientific#120](https://github.com/basvandijk/scientific/issues/120): ```haskell import Data.Scientific main :: IO () main = print (scientific 10 maxBound == scientific 1 minBound) ``` ``` $ ./repro; echo "exit=$?" exit=139 ``` The issue was discovered when Stackage nightly test suites (`genvalidity-hspec-aeson`, `genvalidity-sydtest-aeson`) started segfaulting after upgrading to `scientific-0.3.9.0`: their property tests round-trip `aeson` `Value`s, which produces `Scientific`s with extreme exponents. Versions before `0.3.9.0` did not crash, but `Eq`/`Ord` returned invalid results there instead (the normalisation-based implementation overflows the exponent, reporting `scientific 10 maxBound == scientific 1 minBound` as `True`). The same unchecked read was also reachable through `(+)` and `(-)` on older versions, guarded only by the documented warning about the potential `10^e` blowup — reading outside the cache is not. ## Resolution `scientific-0.3.10.0` computes the logarithms using `Integer`, fixing both the crash and the invalid comparison results, and bounds-checks `magnitude`, so a negative exponent now raises an error instead of reading out of bounds. All entry points (`Eq`, `Ord`, `(+)`, `(-)`) are covered; upgrade to `scientific-0.3.10.0` or later. Note that printing values with exponents close to `maxBound :: Int` remains unreliable due to the inherent `Int` exponent overflow in `normalize`; this limitation is documented upstream and postponed to the next major release. ## Credits Reported by Tom Sydney Kerckhove (@NorfairKing); fixed by Oleg Grenrus (@phadej).

References: https://github.com/basvandijk/scientific/issues/120, https://github.com/NorfairKing/validity/issues/121, https://github.com/basvandijk/scientific/pull/121, https://www.reddit.com/r/haskell/comments/1xbj59g/dont_use_scientific_for_calculations_it_can/