Summary
Observable Timing Discrepancy in pypqc
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://github.com/antoonpurnal/clangover
https://www.github.com/PQClean/PQClean/issues/556
https://www.github.com/pq-crystals/kyber/commit/9b8d30698a3e7449aeb34e62339d4176f11e3c6c
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
GHSA-HVH4-5QR6-3V7R has a CVSS score of 7.8 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. No fixed version is listed yet, so configuration controls and monitoring matter more in the interim.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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No patch is currently available / pending upstream PQClean#556.
Frequently Asked Questions
- What is GHSA-HVH4-5QR6-3V7R? GHSA-HVH4-5QR6-3V7R is a high-severity security vulnerability in pypqc (pip), affecting versions >= 0.0.4, <= 0.0.6.2. No fixed version is listed yet.
- How severe is GHSA-HVH4-5QR6-3V7R? GHSA-HVH4-5QR6-3V7R has a CVSS score of 7.8 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of pypqc are affected by GHSA-HVH4-5QR6-3V7R? pypqc (pip) versions >= 0.0.4, <= 0.0.6.2 is affected.
- Is there a fix for GHSA-HVH4-5QR6-3V7R? No fixed version is listed for GHSA-HVH4-5QR6-3V7R yet. Monitor the advisory for updates and apply mitigations in the interim.
- Is GHSA-HVH4-5QR6-3V7R exploitable, and should I be worried? Whether GHSA-HVH4-5QR6-3V7R is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether GHSA-HVH4-5QR6-3V7R is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.