vm2 before 3.11.7 Denylist Bypass via fs/promises

vm2 through 3.11.6 contains a builtin-module denylist bypass in NodeVM. When the embedder uses the builtin wildcard together with negative entries (e.g. require: { builtin: ['*', '-fs', '-child_process'] }), negative entries are matched by exact module name in lib/builtin.js, so -fs removes only the builtin named fs and does not remove builtin subpaths such as fs/promises. Sandboxed code can therefore call require('fs/promises') or require('node:fs/promises') and reach the promise-based filesystem API despite fs being denied; node: prefix handling is likewise inconsistent (a -node:fs/promises entry does not block require('fs/promises')). Host file creation and writing were confirmed via fsp.writeFile(), and other fs/promises operations (cp, mkdir, rename, rm, rmdir, truncate, read operations, etc.) are also reachable. This issue is fixed in vm2 3.11.7.

Source published

17 Sep 2026 13:46:15 UTC

Source modified

18 Sep 2026 19:35:47 UTC

Observed here

23 Oct 2026 15:48:27 UTC

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CVSS 4.0 · 8.4 CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:L/SC:N/SI:H/SA:L

CVSS 3.1 · 8.5 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:L