CVE-2021-4435 is a high-severity (CVSS 7.8) CWE-426 vulnerability in yarn. A fix is available for yarn — see the affected versions and patch details below.
Yarn untrusted search path vulnerability
Exploitation Status
No confirmed exploitation observed yet
- A successful exploit gives an attacker total control of the affected component, not partial access.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2021-4435.
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
An untrusted search path vulnerability was found in Yarn. When a victim runs certain Yarn commands in a directory with attacker-controlled content, malicious commands could be executed in unexpected ways.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | yarn | all versions | 1.22.13npm install yarn@1.22.13 |
Affected Products
yarnyarnpkgDetection & 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 1.22.13 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-4435 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.
Frequently Asked Questions
Is CVE-2021-4435 in your dependencies?
Find it across npm, including transitive dependencies.