High

Observable Timing Discrepancy in pypqc

  • Disclosed: 05.06.2024
  • Updated: 11.10.2026 12:18

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<!--; it has no known breaking changes-->.

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

Affected software

Click a technology to see all vulnerabilities affecting it.

PlatformPackageVulnerable versionsFixed in
Python (PyPI) pypqc >= 0.0.4, <= 0.0.6.2 no fix

References

CVSS score 8.2/10
CVSS vector
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
Weakness (CWE)
CWE-385, CWE-733
Platform
Python (PyPI)
Package
pypqc
Disclosed
05.06.2024
Updated
11.10.2026 12:18

Sources and licenses

OSV / GitHub Advisory Database - GHSA-hvh4-5qr6-3v7r - CC BY 4.0

Vulnerability history: pypqc

All published vulnerabilities of this package (Python (PyPI)), newest first. Shows whether this is a one-off slip or a package that needs watching.

Total entries
2
First → latest
02.2024 06.2024
Without a fix
1
Exploited in attacks
0

Severity breakdown

  • High 2

Disclosures per year

  1. 2024: 2
  2. 2025: 0
  3. 2026: 0
  1. Observable Timing Discrepancy in pypqc this entry
    High · 8.2 ghsa-hvh4-5qr6-3v7r >= 0.0.4, <= 0.0.6.2 no fix
  2. High · 8.2 ghsa-rc4p-p3j9-6577 >= 0.0.4, < 0.0.6.1 0.0.6.1

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