Vulnerability · Published Sep 27, 2026 · Assigned by VulnCheck
CVE-2026-100721vm2 before 3.12.2 Authorization Bypass via Custom Resolver
Critical 9.0
In plain English
A critical-severity incorrect authorization in vm2 from patriksimek. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.6% (higher than 48% of all known vulnerabilities). Ready-made attack tooling exists: public proof-of-concept code. Fixed versions are available - upgrade the affected package.
Official description
vm2 before 3.12.2 contains an authorization bypass in the NodeVM external-module resolver. When an embedder configures `require.external` with a custom resolver (and `context: 'host'`), `LegacyResolver.customResolve` in lib/resolver-compat.js records the resolved module directory in `this.externals` as `new RegExp('^' + escapeRegExp(resolvedPath))`, without requiring a path separator or end-of-string boundary. Untrusted guest code can therefore require the allowlisted module (e.g. `foo`) and then require the absolute path of a non-allowlisted sibling whose path merely shares the resolved prefix (e.g. `.../node_modules/foo2/index.js`); the sibling passes `isPathAllowedForModule` and is loaded through `hostRequire`, so its top-level code runs in the host process before the exports are wrapped with `vm.readonly`, resulting in a sandbox escape and arbitrary code execution in the host context.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| npm | vm2 | 3.12.2 | GHSA-5h3f-q97h-ccvc |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| patriksimek | vm2 | 0 – before 3.12.2 |
Weakness: CWE-863 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
References
- GitHub Security Advisory (GHSA-5h3f-q97h-ccvc) vendor-advisory
- Patch Commit patch
- Patch Commit patch
- Patch Commit patch
- VulnCheck Advisory: vm2 before 3.12.2 Authorization Bypass via Custom Resolver third-party-advisory