{"id":"CVE-2023-44378","aliases":["GHSA-498w-5j49-vqjg","GO-2023-2098"],"title":"gnark unsoundness in variable comparison / non-unique binary decomposition","summary":"gnark unsoundness in variable comparison / non-unique binary decomposition","severity":"medium","cvss":5.5,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N","vendor":"consensys","product":"github.com/consensys/gnark","ecosystem":"go","affected":["github.com/consensys/gnark < 0.9.0"],"patched":["github.com/consensys/gnark 0.9.0"],"published":"2023-10-04","updated":"2026-09-10","sourceUpdated":"2026-09-10T03:49:24.650234486Z","source":"OSV","sourceUrl":"https://osv.dev/vulnerability/GHSA-498w-5j49-vqjg","references":[{"url":"https://github.com/Consensys/gnark/security/advisories/GHSA-498w-5j49-vqjg"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2023-44378"},{"url":"https://github.com/zkopru-network/zkopru/issues/116"},{"url":"https://github.com/Consensys/gnark/pull/835"},{"url":"https://github.com/Consensys/gnark/commit/59a4087261a6c73f13e80d695c17b398c3d0934f"},{"url":"https://github.com/Consensys/gnark"},{"url":"https://github.com/advisories/GHSA-498w-5j49-vqjg"}],"tags":["osv","go"],"epss":0.00224,"epssPercentile":0.13301,"ingestedAt":"2026-09-12T03:13:01.752Z","slug":"CVE-2023-44378","body":"## Overview\n\n### 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/).\n\n## Affected packages\n\n- `github.com/consensys/gnark < 0.9.0`\n\n## Remediation\n\nUpgrade to a patched release:\n\n- `github.com/consensys/gnark 0.9.0`","depth":"sunlit","depthScore":30,"depthScoreParts":{"impact":30.3,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}