CVE-2020-8131 is a high-severity (CVSS 7.5) Path Traversal vulnerability in yarn. 1 public exploit or proof-of-concept reference is indexed, so weaponization risk is real. A fix is available for yarn — see the affected versions and patch details below.
Path Traversal in Yarn
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
yarnnpmDescription
Arbitrary filesystem write vulnerability in Yarn 1.21.1 and earlier allows attackers to write to any path on the filesystem and potentially lead to arbitrary code execution by forcing the user to install a malicious package.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | yarn | all versions | 1.22.0npm install yarn@1.22.0 |
Affected Products
yarnyarnpkgResearch 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 yarn, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update yarn to 1.22.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-8131 is resolved across your whole dependency graph.
Workarounds
Resolve every user-supplied path to its canonical form and reject anything that escapes the intended directory, and run the component under an account that has no read or write access outside the directory it legitimately serves.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
Normally yarn allows packages to run postinstall scripts which can write arbitrary files to the users system. This vulnerability allows an attacker to better hide the attack and also allow arbitrary file write when postinstall scripts are disabled with the '--ignore-scripts' option of 'yarn install'.
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat Quay 3 | quay/clair-rhel8:v3.4.0-25 | RHSA-2021:0420 |
Frequently Asked Questions
Is CVE-2020-8131 in your dependencies?
Find it across npm, including transitive dependencies.