Observable Timing Discrepancy in pypqc

Impact

kyber512, kyber768, and kyber1024 on Mac OS (or when compiled with clang) only: An attacker able to submit many decapsulation requests against a single private key, and to gain timing information about the decapsulation, could recover the private key. Proof-of-concept exploit exists for a local attacker.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N/E:P/RL:U/RC:C

Patches

No patch is currently available / pending upstream PQClean#556.

Workarounds

No workarounds have been reported. The 0.0.7 -> 0.0.7.1 upgrade, when available, should be a drop-in replacement.

References

https://pqshield.com/pqshield-plugs-timing-leaks-in-kyber-ml-kem-to-improve-pqc-implementation-maturity/

https://github.com/antoonpurnal/clangover

https://www.github.com/PQClean/PQClean/issues/556

https://www.github.com/pq-crystals/kyber/commit/9b8d30698a3e7449aeb34e62339d4176f11e3c6c