vm2: Sandbox escape

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

vm2 is an open source vm/sandbox for Node.js. From 3.9.6 to 3.10.5, vm2's bridge exposes mutable proxies for real host-realm intrinsic prototypes and then forwards sandbox writes into the underlying host objects with otherReflectSet() and otherReflectDefineProperty(), which lets attacker-controlled JavaScript running in a default VM or inherited NodeVM mutate shared host Object.prototype, Array.prototype, and Function.prototype from inside the sandbox This vulnerability is fixed in 3.11.0.

Source published

13 May 2026 17:40:41 UTC

Source modified

7 Sep 2026 12:04:59 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: cve-program · CVE Program Terms of Use. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · 10.0 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:H

vm2 is an open source vm/sandbox for Node.js. From 3.9.6 to 3.10.5, vm2's bridge exposes mutable proxies for real host-realm intrinsic prototypes and then forwards sandbox writes into the underlying host objects with otherReflectSet() and otherReflectDefineProperty(), which lets attacker-controlled JavaScript running in a default VM or inherited NodeVM mutate shared host Object.prototype, Array.prototype, and Function.prototype from inside the sandbox This vulnerability is fixed in 3.11.0.

Source published

May 13, 2026, 5:40:41 PM (timezone not stated)

Source modified

Sep 7, 2026, 12:04:59 PM (timezone not stated)

Observed here

7 Nov 2026 09:37:51 UTC

Source terms

ENISA EUVD · source terms and attribution apply

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: euvd · ENISA EUVD · source terms and attribution apply. Source text is retained; field grouping and change labels are provided by ChangeIntel.

EUVD CVSS 3.1 · 10.0 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:H

vm2 is an open source vm/sandbox for Node.js. From 3.9.6 to 3.10.5, vm2's bridge exposes mutable proxies for real host-realm intrinsic prototypes and then forwards sandbox writes into the underlying host objects with otherReflectSet() and otherReflectDefineProperty(), which lets attacker-controlled JavaScript running in a default VM or inherited NodeVM mutate shared host Object.prototype, Array.prototype, and Function.prototype from inside the sandbox This vulnerability is fixed in 3.11.0.

Source published

13 May 2026 18:16:17 UTC

Source modified

26 Oct 2026 17:10:03 UTC

Observed here

27 Oct 2026 11:12:09 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · [email protected] · Secondary · 10.0 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:H

CVSS 3.1 · 0b0ca135-0b70-47e7-9f44-1890c2a1c46c · Secondary · 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

### Summary vm2's bridge exposes mutable proxies for real host-realm intrinsic prototypes and then forwards sandbox writes into the underlying host objects with otherReflectSet() and otherReflectDefineProperty(), which lets attacker-controlled JavaScript running in a default VM or inherited NodeVM mutate shared host Object.prototype, Array.prototype, and Function.prototype from inside the sandbox. ### Details BaseHandler.apply() unwraps sandbox-controlled receivers and arguments with otherFromThis() / otherFromThisArguments() and then directly invokes the real host function with ret = otherReflectApply(object, context, args), so any default-exposed host function that can surface a prototype getter becomes a prototype-walking primitive ([lib/bridge.js:665-676](https://github.com/patriksimek/vm2/blob/408fc855f1cc1bbc2985b029465ee0e732ada433/lib/bridge.js#L665-L676)). BaseHandler.get() special-cases __proto__ and returns the host-side descriptor or proxy target prototype, which is enough for the attacker to reuse the host __lookupGetter__('__proto__') accessor repeatedly until the walk lands on host Object.prototype, Array.prototype, or Function.prototype ([lib/bridge.js:590-616](https://github.com/patriksimek/vm2/blob/408fc855f1cc1bbc2985b029465ee0e732ada433/lib/bridge.js#L590-L616)). Once the attacker has a proxy to a host intrinsic prototype, BaseHandler.set() performs value = otherFromThis(value); return otherReflectSet(object, key, value) === true;, which writes attacker-controlled data directly into the shared host object instead of keeping the mutation sandbox-local; BaseHandler.defineProperty() repeats the same design at otherReflectDefineProperty(object, prop, otherDesc) for descriptor-based writes ([lib/bridge.js:641-649](https://github.com/patriksimek/vm2/blob/408fc855f1cc1bbc2985b029465ee0e732ada433/lib/bridge.js#L641-L649), [lib/bridge.js:753-774](https://github.com/patriksimek/vm2/blob/408fc855f1cc1bbc2985b029465ee0e732ada433/lib/bridge.js#L753-L774)). Existing validation does not stop the attack because the constructor filter only blocks one dangerous-property access pattern, setPrototypeOf() only blocks prototype replacement rather than ordinary property assignment, and containsDangerousConstructor() only protects one later re-unwrapping path instead of the initial host-prototype write sink ([lib/bridge.js:494-530](https://github.com/patriksimek/vm2/blob/408fc855f1cc1bbc2985b029465ee0e732ada433/lib/bridge.js#L494-L530), [lib/bridge.js:595-610](https://github.com/patriksimek/vm2/blob/408fc855f1cc1bbc2985b029465ee0e732ada433/lib/bridge.js#L595-L610), [lib/bridge.js:660-662](https://github.com/patriksimek/vm2/blob/408fc855f1cc1bbc2985b029465ee0e732ada433/lib/bridge.js#L660-L662)). ### PoC Run the following code snippet and observe that the value of vm2EscapeMarker is polluted: ``` const { VM } = require('vm2'); const vm = new VM(); vm.run(` const g = ({}).__lookupGetter__; const a = Buffer.apply; const p = a.apply(g, [Buffer, ['__proto__']]); const hostObjectProto = p.call(p.call(p.call(p.call(Buffer.of())))); hostObjectProto.vm2EscapeMarker = 'polluted-object-prototype'; `); console.log({}.vm2EscapeMarker) ``` ### Impact Sandbox escape and prototype pollution.

Source published

7 May 2026 04:07:05 UTC

Source modified

14 May 2026 20:51:08 UTC

Observed here

24 Oct 2026 13:17:17 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:H

Publisher rating · CRITICAL