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
fastify-multipartReal-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
Impact
This is a bypass of CVE-2020-8136 (https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-8136).
By providing a name=constructor property it is still possible to crash the application.
The original fix only checks for the key __proto__ (https://github.com/fastify/fastify-multipart/pull/116).
All users are recommended to upgrade
Patches
v5.3.1 includes a patch
Workarounds
No workarounds are possible.
References
Read up https://www.fastify.io/docs/latest/Guides/Prototype-Poisoning/
For more information
If you have any questions or comments about this advisory:
- Open an issue in https://github.com/fastify/fastify-multipart
- Email us at [email protected]
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | fastify-multipart | all versions | 5.3.1 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for fastify-multipart. 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 fastify-multipart to 5.3.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-qh73-qc3p-rjv2 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-qh73-qc3p-rjv2 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-qh73-qc3p-rjv2. 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-qh73-qc3p-rjv2 in your dependencies?
O3 detects GHSA-qh73-qc3p-rjv2 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.