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. A fix is available for reffers — see the affected versions and patch details below.
Data races in reffers
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2020-36203 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 385,738 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
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 | 0.6.1cargo update -p reffers --precise 0.6.1 |
Affected Products
reffersreffers_projectResearch 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, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
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
Constrain what reaches the vulnerable code: limit the size and shape of untrusted input, isolate the affected component in a sandboxed or least-privileged process, and enable the platform's memory-safety mitigations (ASLR, stack protector, hardened allocator) so an out-of-bounds access is more likely to fail closed than to be exploitable.
Frequently Asked Questions
Is CVE-2020-36203 in your dependencies?
Find it across crates.io, including transitive dependencies.