vm2 before 3.12.1 Sandbox Escape RCE via Non-Strict Host Function (CVE-2026-93603)

What is affected, what to do

A flaw was found in vm2. This vulnerability allows an attacker who can execute untrusted script within the sandbox to achieve arbitrary code execution on the underlying host system by escaping sandbox containment.

Update Patriksimek Vm2 to version 3.12.1.

Affected

• Patriksimek Vm2 lt *..3.12.1

Fixed in

• Patriksimek Vm2 3.12.1

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Metrics

Detection rules

No NEOSEC detection rule is available for this vulnerability yet.

Classification under NIS2 and CRA

Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

NIS2

NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

Read in glossary

High technical severity: assess and remediate the vulnerability in vulnerability handling under Art. 21(2)(e) NIS2 and document the decision.

CRA

The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

Read in glossary

From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.

ISO/IEC 27001

ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

Read in glossary

Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

Description

A flaw was found in vm2. This vulnerability allows an attacker who can execute untrusted script within the sandbox to achieve arbitrary code execution on the underlying host system by escaping sandbox containment. The issue occurs because vm2 fails to properly handle function calls lacking an object receiver, causing the JavaScript runtime to expose the host environment's global object to the sandboxed code.

Source: redhat_csaf, BSI WID Portal, BSI CSAF, cvelistv5, NVD (NIST)

Vendors and products

• Open Source Vm2
• Patriksimek Vm2

Weakness classes (CWE)

• CWE-94Improper Control of Generation of Code ('Code Injection')

  Base

  The product constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment.

  Entry at MITRE CWE-94

References & sources

• github.comGitHub Security Advisory (GHSA-j89j-5m6r-cr2q)Vendor advisory
• vulncheck.comVulnCheck Advisory: vm2 before 3.12.1 Sandbox Escape RCE via Non-Strict Host FunctionThird-party advisory

Changes to this CVE

Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).

1. 22.09.2026Record modifiedCISA ADP

   CISA assessment (SSVC): exploitation: proof of concept, automatable: yes

   New references:

   • https://github.com/patriksimek/vm2/security/advisories/GHSA-j89j-5m6r-cr2q
   Show 2 original changes

   Individual changes of this event as published by NVD

   Type	Action	Before	After
   Reference	added	—	https://github.com/patriksimek/vm2/security/advisories/GHSA-j89j-5m6r-cr2q
   SSVC assessment	added	—	{"id":"CVE-2026-93603","role":"CISA Coordinator","options":[{"exploitation":"poc"},{"automatable":"yes"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-09-22T14:25:04.925932Z"}

   Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0

2. 18.09.2026ReceivedVulnCheck

   CVSS V4.0: AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H

   CVSS V3.1: AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

   Weakness type: CWE-94

   Description added or changed

   New references:

   • https://github.com/patriksimek/vm2/security/advisories/GHSA-j89j-5m6r-cr2q
   • https://www.vulncheck.com/advisories/vm2-before-3.12.1-sandbox-escape-rce-via-non-strict-host-function
   Show 7 original changes

   Individual changes of this event as published by NVD

   Type	Action	Before	After
   Description	added	—	vm2 through 3.12.0 (fixed in 3.12.1) does not correctly handle a nullish `this` receiver in the apply trap of its bridge (lib/bridge.js): when sandboxed code calls a host-provided non-strict (sloppy-mode) function without a receiver — e.g. `fn()`, a detached method, `fn.call()`, `fn.apply(undefined)`, `Reflect.apply(fn, undefined, [])`, or `fn.bind()()` — the undefined receiver is passed straight through to the host call, and V8 substitutes the host realm's global object for `this`. vm2 then wraps and returns that object to the sandbox, giving sandboxed script a live proxy of the host global. This allows a complete sandbox escape: untrusted script can reach `process` and execute arbitrary code/commands on the host (for example via `process.getBuiltinModule('child_process').execSync`). Exploitation requires that the embedding application expose at least one non-strict host function to the sandbox; strict-mode and ES module host functions are not affected.
   CVSS	added	—	AV:N/AC:L/AT:N/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
   CVSS	added	—	AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
   Weakness type (CWE)	added	—	CWE-94
   Affected versions (publisher)	added	—	New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/93xxx/CVE-2026-93603.json">CVE-2026-93603</a>
   Reference	added	—	https://github.com/patriksimek/vm2/security/advisories/GHSA-j89j-5m6r-cr2q
   Reference	added	—	https://www.vulncheck.com/advisories/vm2-before-3.12.1-sandbox-escape-rce-via-non-strict-host-function

   Source identifier: disclosure@vulncheck.com