CVE-2026-100721: vm2: NodeVM custom resolution bypasses external path boundaries
At source revision 91034466bfb7f56b95fd48083ec6ca36d058f164 of vm2 3.11.8, an untrusted NodeVM guest can turn one allowlisted custom-resolved module into authorization for a separate file whose path merely shares the resolved path’s string prefix. LegacyResolver.customResolve stores the resolved path in this.externals as ^<path> without an end or separator boundary; a later absolute require of a sibling such as foo2/index.js therefore passes the external check and is loaded through hostRequire when the configured context is host. The decisive attack loaded foo as FOO_OK and then executed the prefix-sharing sibling, which returned PREFIX_PWN after invoking child_process; an otherwise identical control denied the sibling with ENOTFOUND.
References
- github.com/advisories/GHSA-5h3f-q97h-ccvc
- github.com/patriksimek/vm2/commit/6ac3916da84e060c403e407b6b6318fcc66b0e72
- github.com/patriksimek/vm2/commit/91034466bfb7f56b95fd48083ec6ca36d058f164
- github.com/patriksimek/vm2/commit/ab4ee7d803e8c80155e9eb3672226bddbca4aa9c
- github.com/patriksimek/vm2/commit/fb4977f6211da6cadffdf1f3a2017a826a21c51f
- github.com/patriksimek/vm2/releases/tag/v3.12.2
- github.com/patriksimek/vm2/security/advisories/GHSA-5h3f-q97h-ccvc
- nvd.nist.gov/vuln/detail/CVE-2026-100721
- www.vulncheck.com/advisories/vm2-before-3.12.2-authorization-bypass-via-custom-resolver
Code Behaviors & Features
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