# CVE-2026-47209: vm2: Bridge Proxy set trap ignores receiver parameter, enabling host object property injection via prototype chain

> Attackers can inject properties into host objects via prototype chain manipulation, bypassing sandbox restrictions and potentially executing code.

- **Severity:** High 8.6 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 12 Jun 2026
- **Updated:** 12 Jun 2026
- **Also known as:** ECHO-7db5-a96e-2943, GHSA-c4cf-2hgv-2qv6, MINI-vpj7-8pmf-r3jc, ROOT-APP-NPM-CVE-2026-47209

## What is CVE-2026-47209?

CVE-2026-47209 is a high-severity code injection vulnerability in patriksimek vm2, published on 12 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

vm2 is an open source vm/sandbox for Node.js. Prior to version 3.11.4, the BaseHandler.set trap in bridge.js (line 1231) ignores the receiver parameter and unconditionally writes to the host target object. Per the Proxy set trap specification, when receiver !== proxy (e.g., when a child object inherits from the proxy via Object.create), the property assignment should create an own property on the receiver, not on the proxy target. The current implementation always calls otherReflectSet(object, key, value) against the host target, causing all inherited property writes to leak through to the host object. This bug provides an alternative attack vector for writing dangerous cross-realm Symbol keys (e.g., nodejs.util.promisify.custom) to host objects, bypassing any future per-trap isDangerousCrossRealmSymbol guard on the direct set path. This issue has been patched in version 3.11.4.

Weakness: CWE-693 (Protection Mechanism Failure)

## Which versions are affected by CVE-2026-47209?

2 open source packages ship an affected version, including vm2.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `vm2` | npm | All versions | 3.11.4 |
| `vm2` | npm | All versions | 3.11.4 |

## How do I fix CVE-2026-47209?

Upgrade vm2 to 3.11.4 or later.

## Is CVE-2026-47209 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-47209 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-47209 and fix it if it is affected.

What it is: CVE-2026-47209 is a high-severity code injection vulnerability in patriksimek vm2, published on 12 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-47209 exists.

Affected packages and fixed versions:
- vm2 (npm): affected all versions; fixed in 3.11.4
- vm2 (npm): affected all versions; fixed in 3.11.4

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-47209/ (Markdown: https://insights.sbomify.com/CVE-2026-47209/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-47209
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-47209
- OSV: https://osv.dev/vulnerability/CVE-2026-47209

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-47209/
Summaries are generated and may contain mistakes; the official description above is the record.