{"id":"CVE-2026-100721","sourceIdentifier":"disclosure@vulncheck.com","published":"2026-09-27T02:17:17.547","lastModified":"2026-09-28T17:17:46.057","vulnStatus":"Deferred","cveTags":[],"descriptions":[{"lang":"en","value":"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":[{"source":"disclosure@vulncheck.com","affectedData":[{"vendor":"patriksimek","product":"vm2","defaultStatus":"unaffected","packageURL":"pkg:npm/vm2","versions":[{"version":"0","lessThan":"3.12.2","versionType":"semver","status":"affected"},{"version":"3.12.2","versionType":"semver","status":"unaffected"}]}]}],"metrics":{"cvssMetricV40":[{"source":"disclosure@vulncheck.com","type":"Secondary","cvssData":{"version":"4.0","vectorString":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","baseScore":9.5,"baseSeverity":"CRITICAL","attackVector":"NETWORK","attackComplexity":"LOW","attackRequirements":"PRESENT","privilegesRequired":"NONE","userInteraction":"NONE","vulnConfidentialityImpact":"HIGH","vulnIntegrityImpact":"HIGH","vulnAvailabilityImpact":"HIGH","subConfidentialityImpact":"HIGH","subIntegrityImpact":"HIGH","subAvailabilityImpact":"HIGH","exploitMaturity":"NOT_DEFINED","confidentialityRequirement":"NOT_DEFINED","integrityRequirement":"NOT_DEFINED","availabilityRequirement":"NOT_DEFINED","modifiedAttackVector":"NOT_DEFINED","modifiedAttackComplexity":"NOT_DEFINED","modifiedAttackRequirements":"NOT_DEFINED","modifiedPrivilegesRequired":"NOT_DEFINED","modifiedUserInteraction":"NOT_DEFINED","modifiedVulnConfidentialityImpact":"NOT_DEFINED","modifiedVulnIntegrityImpact":"NOT_DEFINED","modifiedVulnAvailabilityImpact":"NOT_DEFINED","modifiedSubConfidentialityImpact":"NOT_DEFINED","modifiedSubIntegrityImpact":"NOT_DEFINED","modifiedSubAvailabilityImpact":"NOT_DEFINED","Safety":"NOT_DEFINED","Automatable":"NOT_DEFINED","Recovery":"NOT_DEFINED","valueDensity":"NOT_DEFINED","vulnerabilityResponseEffort":"NOT_DEFINED","providerUrgency":"NOT_DEFINED"}}],"cvssMetricV31":[{"source":"disclosure@vulncheck.com","type":"Secondary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H","baseScore":9.0,"baseSeverity":"CRITICAL","attackVector":"NETWORK","attackComplexity":"HIGH","privilegesRequired":"NONE","userInteraction":"NONE","scope":"CHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"},"exploitabilityScore":2.2,"impactScore":6.0}],"ssvcV203":[{"source":"134c704f-9b21-4f2e-91b3-4a467353bcc0","ssvcData":{"timestamp":"2026-09-28T16:50:50.404410Z","id":"CVE-2026-100721","options":[{"exploitation":"poc"},{"automatable":"no"},{"technicalImpact":"total"}],"role":"CISA Coordinator","version":"2.0.3"}}]},"weaknesses":[{"source":"disclosure@vulncheck.com","type":"Secondary","description":[{"lang":"en","value":"CWE-863"}]}],"references":[{"url":"https://github.com/patriksimek/vm2/commit/6ac3916da84e060c403e407b6b6318fcc66b0e72","source":"disclosure@vulncheck.com"},{"url":"https://github.com/patriksimek/vm2/commit/91034466bfb7f56b95fd48083ec6ca36d058f164","source":"disclosure@vulncheck.com"},{"url":"https://github.com/patriksimek/vm2/commit/ab4ee7d803e8c80155e9eb3672226bddbca4aa9c","source":"disclosure@vulncheck.com"},{"url":"https://github.com/patriksimek/vm2/security/advisories/GHSA-5h3f-q97h-ccvc","source":"disclosure@vulncheck.com"},{"url":"https://www.vulncheck.com/advisories/vm2-before-3.12.2-authorization-bypass-via-custom-resolver","source":"disclosure@vulncheck.com"}]}