{"id":"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\n\n`scientific-0.3.9.0` reimplemented `Eq` and `Ord` without normalising their\narguments. The new implementation short-circuits on\n`integerLog10' c + e` computed in `Int`, which overflows when the base-10\nexponent is close to `maxBound :: Int`. The overflowed comparison then falls\nthrough to `magnitude (e1 - e2)`, where the exponent difference overflows to a\nnegative `Int` as well. `magnitude` indexed its cached power-of-ten array\nwithout a bounds check, so the negative index performed an out-of-bounds read\nand the process died with `SIGSEGV`.\n\nWith `scientific-0.3.9.0` (GHC 9.10.3, x86_64-linux), as reported in\n[basvandijk/scientific#120](https://github.com/basvandijk/scientific/issues/120):\n\n```haskell\nimport Data.Scientific\n\nmain :: IO ()\nmain = print (scientific 10 maxBound == scientific 1 minBound)\n```\n\n```\n$ ./repro; echo \"exit=$?\"\nexit=139\n```\n\nThe issue was discovered when Stackage nightly test suites\n(`genvalidity-hspec-aeson`, `genvalidity-sydtest-aeson`) started segfaulting\nafter upgrading to `scientific-0.3.9.0`: their property tests round-trip\n`aeson` `Value`s, which produces `Scientific`s with extreme exponents.\n\nVersions before `0.3.9.0` did not crash, but `Eq`/`Ord` returned invalid\nresults there instead (the normalisation-based implementation overflows the\nexponent, reporting `scientific 10 maxBound == scientific 1 minBound` as\n`True`). The same unchecked read was also reachable through `(+)` and `(-)` on\nolder versions, guarded only by the documented warning about the potential\n`10^e` blowup — reading outside the cache is not.\n\n## Resolution\n\n`scientific-0.3.10.0` computes the logarithms using `Integer`, fixing both the\ncrash and the invalid comparison results, and bounds-checks `magnitude`, so a\nnegative exponent now raises an error instead of reading out of bounds. All\nentry points (`Eq`, `Ord`, `(+)`, `(-)`) are covered; upgrade to\n`scientific-0.3.10.0` or later.\n\nNote that printing values with exponents close to `maxBound :: Int` remains\nunreliable due to the inherent `Int` exponent overflow in `normalize`; this\nlimitation is documented upstream and postponed to the next major release.\n\n## Credits\n\nReported by Tom Sydney Kerckhove (@NorfairKing); fixed by Oleg Grenrus\n(@phadej).\n","modified":"2026-11-03T22:45:02.613041440Z","published":"2026-11-03T22:32:58Z","related":["HSEC-2026-0011"],"database_specific":{"repository":"https://github.com/haskell/security-advisories","home":"https://github.com/haskell/security-advisories","osvs":"https://raw.githubusercontent.com/haskell/security-advisories/refs/heads/generated/osv-export"},"references":[{"type":"REPORT","url":"https://github.com/basvandijk/scientific/issues/120"},{"type":"REPORT","url":"https://github.com/NorfairKing/validity/issues/121"},{"type":"FIX","url":"https://github.com/basvandijk/scientific/pull/121"},{"type":"DISCUSSION","url":"https://www.reddit.com/r/haskell/comments/1xbj59g/dont_use_scientific_for_calculations_it_can/"}],"affected":[{"package":{"name":"scientific","ecosystem":"Hackage","purl":"pkg:hackage/scientific"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0.3.9.0"},{"fixed":"0.3.10.0"}]}],"versions":["0.3.9.0"],"database_specific":{"human_link":"https://github.com/haskell/security-advisories/tree/main/advisories/published/2026/HSEC-2026-0012.md","osv":"https://raw.githubusercontent.com/haskell/security-advisories/refs/heads/generated/osv-export/2026/HSEC-2026-0012.json","source":"https://github.com/haskell/security-advisories/blob/generated/osv-export/2026/HSEC-2026-0012.json"},"severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H"}]}],"schema_version":"1.9.2"}