gnark affected by denial of service when computing scalar multiplication using fake-GLV algorithm

### Impact For optimizing the scalar multiplication algorithm in circuit for some curves, gnark uses fake-GLV algorithm in case the curve doesn't support true-GLV. For this to work, we need to compute the scalar decomposition using the Half GCD method in gnark-crypto. However, for some of the inputs the algorithm didn't converge quickly enough. In case the prover accepts untrusted witness, it could lead to denial of service as the prover gets stuck in a very slowly converging loop. Thanks to @feltroidprime for reporting the issue and proposing a fix. ### Patches The issue has been patched in gnark-crypto commit https://github.com/Consensys/gnark-crypto/commit/56600883e0e9f9b159e9c7000b94e76185ec3d0d. The dependency update is implemented in gnark commit https://github.com/Consensys/gnark/commit/68be6cede36e387ab760725beabd3c96cc94e6dc. ### Workarounds This update doesn't require recompiling the circuits as the issue is in the hint function. The users can update the gnark-crypto dependency to the fixed version. ### References * See bug report https://github.com/Consensys/gnark/issues/1483 * Fake GLV description https://ethresear.ch/t/fake-glv-you-dont-need-an-efficient-endomorphism-to-implement-glv-like-scalar-multiplication-in-snark-circuits/20394

Source published

29 Aug 2025 20:20:13 UTC

Source modified

17 Sep 2025 17:42:12 UTC

Observed here

24 Oct 2026 13:19:41 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Publisher rating · HIGH