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Advisory record · RUSTSEC-2026-0288

cosmian_kyber: AVX2 backend skips Fujisaki-Okamoto implicit rejection, enabling chosen-ciphertext key recovery

CVSS 7.4 High

Published by OSV at 16 Aug 2026, 12:00 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

PackageEcosystemAffectedFixed in
cosmian_kybercrates.io>=0.0.0-0No fixed version yet
Identifiers
RUSTSEC-2026-0288
Published
16 Aug 2026
Updated
18 Sept 2026

Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

cosmian_kyber builds with the avx2 feature on x86_64 skip Fujisaki-Okamoto implicit rejection during decapsulation. An attacker who can submit ciphertexts under a reused key pair and observe the resulting shared secrets can recover the static secret key. No fixed version is listed; avoid the avx2 feature and do not reuse key pairs across decapsulations.

Written 8 Nov 2026.

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

ScoreRatingCVSSVectorSource
7.4 High 3.1 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N OSV
  • CISA KEV Not listed.
  • EPSS No score.

Timeline

  1. 31 Oct 2026, 15:17 UTC First seen by agentprime
  2. 31 Oct 2026, 15:17 UTC Confirmed by OSV

Sources

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.