Summary
Misuse of Reference and other transferable APIs may lead to access to nodejs isolate
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.
Impact
CVE-2021-21413 has a CVSS score of 8.0 (High). The vector is reachable from an adjacent network, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (4.0.0); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Frequently Asked Questions
- What is CVE-2021-21413? CVE-2021-21413 is a high-severity security vulnerability in isolated-vm (npm), affecting versions < 4.0.0. It is fixed in 4.0.0.
- How severe is CVE-2021-21413? CVE-2021-21413 has a CVSS score of 8.0 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of isolated-vm are affected by CVE-2021-21413? isolated-vm (npm) versions < 4.0.0 is affected.
- Is there a fix for CVE-2021-21413? Yes. CVE-2021-21413 is fixed in 4.0.0. Upgrade to this version or later.
- Is CVE-2021-21413 exploitable, and should I be worried? Whether CVE-2021-21413 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2021-21413 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2021-21413? Upgrade
isolated-vmto 4.0.0 or later.