8.6

CVSS Score

3.1

-

CVSS Score

Basic Information

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CVE-2026-47139

CVE-2026-47139: vm2: NodeVM network builtin exclusions bypass via internal _http_client and _http_server

vm2 is an open source vm/sandbox for Node.js. Prior to version 3.11.4, NodeVM supports excluding public network builtins from the wildcard builtin option. With this configuration direct access to http, https, http2, net, dgram, tls, dns, and dns/promises is blocked. However, Node.js also exposes underscored internal HTTP builtins such as _http_client and _http_server. These are not blocked when the public modules are excluded. Sandboxed code can use these internal builtins to make outbound HTTP requests and open listening HTTP sockets even though the public network modules are denied. This issue has been patched in version 3.11.4.

(GitHub Advisory)

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CVE-2026-47139

CVE-2026-47139:

8.6

CVSS Score

3.1

-

CVSS Score

Basic Information

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Technical Details

SSVC / BOD 26-04 ↗

Exploitation pocAutomatable YesTech Impact Partial

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Package Name	Ecosystem	Vulnerable Versions	First Patched Version
vm2	npm	<= 3.11.3	3.11.4

Technical Details

Vulnerability Intelligence
Miggo AI

Root Cause Analysis

The vulnerability exists in the vm2 library's NodeVM component, specifically in how it handles the wildcard '*' option for built-in modules. The root cause is an incomplete filter applied during the initialization of the BUILTIN_MODULES constant in lib/builtin.js. This constant was populated with modules from require('module').builtinModules but failed to exclude undocumented, underscored modules (e.g., _http_client, _http_server) which provide direct access to network primitives.

The function makeBuiltinsFromLegacyOptions in lib/builtin.js uses this flawed BUILTIN_MODULES list to expand the '*' wildcard when processing the require.builtin configuration. Consequently, if a user configured NodeVM with builtin: ['*', '-http', '-net'] to restrict network access, the wildcard expansion would still grant access to the underscored network-capable modules. This allowed sandboxed code to bypass the intended security policy and perform network operations, leading to a Server-Side Request Forgery (SSRF) vulnerability.

The patch rectifies this by adding !s.startsWith('_') to the filter for BUILTIN_MODULES, ensuring that these internal modules are not included in wildcard expansions. The function makeBuiltinsFromLegacyOptions is identified as the key vulnerable function because it is responsible for processing the configuration that enables the vulnerability.

Vulnerable functions

makeBuiltinsFromLegacyOptions

lib/builtin.js

This function is responsible for processing the `require.builtin` option when a `NodeVM` is created. When the `builtin` array contains a wildcard `'*'`, this function uses the `BUILTIN_MODULES` constant to generate the list of allowed modules. Prior to the patch, `BUILTIN_MODULES` was not filtered to exclude underscored internal Node.js modules (e.g., `_http_client`). As a result, `makeBuiltinsFromLegacyOptions` would incorrectly include these network-capable modules in the sandbox's allowlist, even when public network modules like `http` were explicitly excluded. This allowed sandboxed code to bypass network restrictions.

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Miggo AI

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WAF Protection Rules

WAF Rule

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Reasoning

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