CVE-2020-36203 is a medium-severity (CVSS 4.7) CWE-362 vulnerability in reffers. 1 public exploit reference exists, so weaponization risk is real. O3 Security confirms whether CVE-2020-36203 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Data races in reffers
Real-World Exposure
reffersReal-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
ARefss<'a, V> is a type that is assumed to contain objects that are Send + Sync.
In the affected versions of this crate, Send/Sync traits are unconditionally implemented for ARefss<'a, V>.
By using the ARefss::map() API, we can insert a !Send or !Sync object into ARefss<'a, V>. After that, it is possible to create a data race to the inner object of ARefss<'a, V>, which can lead to undefined behavior & memory corruption.
The flaw was corrected in commit 6dd7ca0 by adding trait bound V: Send + Sync to ARefss::map() API.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🦀crates.io | reffers | all versions | 0.6.1 |
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 reffers. 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 reffers to 0.6.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-36203 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 CVE-2020-36203 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 CVE-2020-36203. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2020-36203 in your dependencies?
O3 detects CVE-2020-36203 across crates.io dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.