{"id":"CVE-2023-44378","aliases":["GHSA-498w-5j49-vqjg","GO-2023-2098"],"url":"https://o3.security/vulnerability/CVE-2023-44378","summary":"gnark vulnerable to unsoundness in variable comparison/non-unique binary decomposition","details":"### Impact\n\nFor some in-circuit values, it is possible to construct two valid decomposition to bits. In addition to the canonical decomposition of `a`, for small values there exists a second decomposition for `a+r` (where `r` is the modulus the values are being reduced by). The second decomposition was possible due to overflowing the field where the values are defined.\n\nInternally, the comparison methods `frontend.API.Cmp` and `frontend.API.IsLess` used binary decomposition and checked the bitwise differences. This allows a malicious prover to construct a valid proof for a statement `a < b` even if `a > b`.\n\nThe issue impacts all users using `API.Cmp` or `API.IsLess` methods. Additionally, it impacts the users using `bits.ToBinary` or `API.ToBinary` methods if full-width decomposition is requested (the default behaviour if no options are given).\n\nThe issues does not impact comparison methods in field emulation (package `std/math/emulated`) and dedicated comparison package (`std/math/cmp`).\n\n### Patches\n\nFix has been implemented in pull request #835 and merged in commit 59a4087261a6c73f13e80d695c17b398c3d0934f to master branch. The release v0.9.0 and onwards include the fix.\n\nThe fix added additional comparison of the decomposed bit-vector to the modulus of the in-circuit values.  \n\n### Workarounds\n\nUpgrading to version v0.9.0 should fix the issue without needing to change the calls to value comparison methods.\n\nAlternatively, users can use the `std/math/cmp` gadget, which additionally allows to bound the number of bits being compared, making the comparisons more efficient if the bound on the absolute difference of the values is known.\n\n### References\n\n* https://github.com/Consensys/gnark/pull/835\n* https://github.com/zkopru-network/zkopru/issues/116\n* https://github.com/iden3/circomlib/pull/48\n\n### Acknowledgement\n\nThe vulnerability was reported by [Marcin Kostrzewa](https://github.com/kustosz) @ [Reilabs](https://reilabs.io/).","published":"2023-10-09T13:33:54.973Z","modified":"2026-09-05T03:45:11.767364288Z","cvss":{"score":7.1,"severity":"HIGH","vector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N"},"epss":{"score":0.00224,"percentile":0.12859,"asOf":"2026-08-26"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Go","name":"github.com/consensys/gnark","fixedVersion":"0.9.0"}],"fix":{"url":"https://github.com/Consensys/gnark/commit/59a4087261a6c73f13e80d695c17b398c3d0934f","label":"Consensys/gnark@59a4087"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2023/44xxx/CVE-2023-44378.json"},{"type":"ADVISORY","url":"https://github.com/Consensys/gnark/security/advisories/GHSA-498w-5j49-vqjg"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2023-44378"},{"type":"REPORT","url":"https://github.com/zkopru-network/zkopru/issues/116"},{"type":"FIX","url":"https://github.com/Consensys/gnark/commit/59a4087261a6c73f13e80d695c17b398c3d0934f"},{"type":"WEB","url":"https://github.com/Consensys/gnark/pull/835"},{"type":"PACKAGE","url":"https://github.com/Consensys/gnark"},{"type":"ADVISORY","url":"https://github.com/advisories/GHSA-498w-5j49-vqjg"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-09-05T03:45:11.767364288Z"}}