CVE-2021-21413 is a critical-severity (CVSS 9.6) CWE-913 vulnerability in isolated-vm. A fix is available for isolated-vm — see the affected versions and patch details below.
Misuse of `Reference` and other transferable APIs may lead to access to nodejs isolate
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.
How urgent is this, really
CVE-2021-21413 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 378,567 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
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.
isolated-vmnpmDescription
Versions of isolated-vm before v4.0.0, and especially before v3.0.0, have API pitfalls which may make it easy for implementers to expose supposed secure isolates to the permissions of the main nodejs isolate.
Reference objects allow access to the underlying reference's full prototype chain. In an environment where the implementer has exposed a Reference instance to an attacker they would be able to use it to acquire a Reference to the nodejs context's Function object.
Similar application-specific attacks could be possible by modifying the local prototype of other API objects.
Access to NativeModule objects could allow an attacker to load and run native code from anywhere on the filesystem. If combined with, for example, a file upload API this would allow for arbitrary code execution.
To address these issues the following changes were made in v4.0.0:
- Documentation was updated with more explicit guidelines on building secure applications.
Referenceinstances will no longer follow prototype chains by default, nor will they invoke accessors or proxies.- All
isolated-vmAPI prototypes are now immutable. NativeModuleconstructor may only be invoked from a nodejs isolate.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | isolated-vm | all versions | 4.0.0npm install isolated-vm@4.0.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for isolated-vm, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update isolated-vm to 4.0.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-21413 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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2021-21413 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2021-21413. 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-2021-21413 in your dependencies?
O3 Security finds CVE-2021-21413 across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.