GHSA-x5j2-g63m-f8g4 is a high-severity (CVSS 7.4) vulnerability in pqc_kyber. No vendor fix is recorded yet; mitigation options are listed below.
pqc_kyber KyberSlash: division timings depending on secrets
Real-World Exposure
pqc_kyberReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects crates.io packages — download data is not available via public APIs for these ecosystems.
Description
Various Kyber software libraries in various environments leak secret information into timing, specifically because
- these libraries include a line of code that divides a secret numerator by a public denominator,
- the number of CPU cycles for division in various environments varies depending on the inputs to the division, and
- this variation appears within the range of numerators used in these libraries.
The KyberSlash pages track which Kyber libraries have this issue, and include a FAQ about the issue.
Author
The KyberSlash pages were written by Daniel J. Bernstein. The FAQ originally said "I", but some people seemed to have trouble finding this authorship statement, so the FAQ now says "Bernstein" instead.
URL
The permanent link for the KyberSlash pages is https://kyberslash.cr.yp.to.
Mitigation status in pqc_kyber crate
The issues has not been resolved in the pqc_kyber crate. A third-party fork that mitigates this attack vector has been published as safe_pqc_kyber.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🦀crates.io | pqc_kyber | all versions | No fix |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for pqc_kyber, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Remediation status
No patched version of pqc_kyber has shipped for GHSA-x5j2-g63m-f8g4 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
Mitigate without a patch
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-x5j2-g63m-f8g4 can be triaged on real exposure rather than presence alone.
Tailored to GHSA-x5j2-g63m-f8g4. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-x5j2-g63m-f8g4 in your dependencies?
O3 Security finds GHSA-x5j2-g63m-f8g4 across crates.io dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.