GHSA-mwcw-c2x4-8c55
MEDIUMPredictable results in nanoid generation when given non-integer values
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Blast Radius
nanoid📦nanoidReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects npm packages — download data is not available via public APIs for these ecosystems.
Description
When nanoid is called with a fractional value, there were a number of undesirable effects:
- in browser and non-secure, the code infinite loops on while (size--)
- in node, the value of poolOffset becomes fractional, causing calls to nanoid to return zeroes until the pool is next filled
- if the first call in node is a fractional argument, the initial buffer allocation fails with an error
Version 3.3.8 and 5.0.9 are fixed.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | nanoid | ≥ 4.0.0&&< 5.0.9 | 5.0.9 |
| 📦npm | nanoid | all versions | 3.3.8 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for nanoid. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update nanoid to 5.0.9 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-mwcw-c2x4-8c55 is resolved across your whole dependency graph.
Workarounds
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 pinpoints whether GHSA-mwcw-c2x4-8c55 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-mwcw-c2x4-8c55. 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-mwcw-c2x4-8c55 in your dependencies?
O3 detects GHSA-mwcw-c2x4-8c55 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.