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Public proof of conceptFix available

CVE-2021-21413

A public proof of concept exists; no exploitation attested.

  • Published2021-03-30
  • Fixed in4.0.0
  • WeaknessCWE-913

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

isolated-vm is a library for nodejs which gives you access to v8's Isolate interface. Versions of isolated-vm before v4.0.0 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. This is addressed in v4.0.0 through a series of related changes.

Timeline

dates in UTC
  1. 2021-03-3023:15CVE publishedNVD
  2. 2026-10-2319:23First public proof of conceptPoC-in-GitHub

Observed activity

isMalicious corpus · updated 2026-10-23 21:37 UTC
Indicators tagged with this CVE, per day0 indicators over 7 days
Block these indicators
  • Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2021-21413?format=txt
  • CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-21413?format=csv
  • TAXII collection of exploited CVEs
  • The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD · OSV
Isolated-vm project isolated-vm
BranchAffectedFixed in
4.0< 4.0.04.0.0

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

  1. Update Isolated-vm project isolated-vm to 4.0.0

Advisories and patches

Detection

read 2026-10-23 19:23 UTC
Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof-of-concept repositories
1 repository, unverifiedsm1ee/CVE-2021-21413
PoC-in-GitHub

Sources

  • CNACVSS 3.18read 2026-10-23
  • NVDCVSS 3.19.6read 2026-10-23
  • NVDCVSS 2.05.8read 2026-10-23
  • CNAweakness (CWE)CWE-913read 2026-10-23
  • FIRST EPSSEPSS score0.7 %2026-10-23
  • PoC-in-GitHubproof of concept1read 2026-10-23
  • OSVaffected packages—

Technical details

CVSS v3 Vector
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
Published
2021-03-30
Last Modified
2026-06-17
NVD status
Modified

Frequently asked questions

What is CVE-2021-21413?

isolated-vm is a library for nodejs which gives you access to v8's Isolate interface. Versions of isolated-vm before v4.0.0 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. This is addressed in v4.0.0 through a series of related changes.

Is CVE-2021-21413 actively exploited?

Active exploitation of CVE-2021-21413 has not been confirmed. Its EPSS score was 0.7% on 2026-10-23, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-21413?

CVE-2021-21413 has a CVSS v3 base score of 9.6 (CRITICAL severity), with vector string CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H.

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