fix: __proto__ pollution (#4885)

rahulyadav5524 · web-flow · commit 0d7ec33ff375 · 2026-03-12T22:12:50.000+01:00
diff --git a/lib/dispatcher/balanced-pool.js b/lib/dispatcher/balanced-pool.js
@@ -14,7 +14,7 @@ const {
 } = require('./pool-base')
 const Pool = require('./pool')
 const { kUrl } = require('../core/symbols')
-const { parseOrigin } = require('../core/util')
+const util = require('../core/util')
 const kFactory = Symbol('factory')
 
 const kOptions = Symbol('options')
@@ -56,7 +56,10 @@ class BalancedPool extends PoolBase {
 
     super()
 
-    this[kOptions] = opts
+    this[kOptions] = { ...util.deepClone(opts) }
+    this[kOptions].interceptors = opts.interceptors
+      ? { ...opts.interceptors }
+      : undefined
     this[kIndex] = -1
     this[kCurrentWeight] = 0
 
@@ -76,7 +79,7 @@ class BalancedPool extends PoolBase {
   }
 
   addUpstream (upstream) {
-    const upstreamOrigin = parseOrigin(upstream).origin
+    const upstreamOrigin = util.parseOrigin(upstream).origin
 
     if (this[kClients].find((pool) => (
       pool[kUrl].origin === upstreamOrigin &&
@@ -85,7 +88,7 @@ class BalancedPool extends PoolBase {
     ))) {
       return this
     }
-    const pool = this[kFactory](upstreamOrigin, Object.assign({}, this[kOptions]))
+    const pool = this[kFactory](upstreamOrigin, this[kOptions])
 
     this[kAddClient](pool)
     pool.on('connect', () => {
@@ -125,7 +128,7 @@ class BalancedPool extends PoolBase {
   }
 
   removeUpstream (upstream) {
-    const upstreamOrigin = parseOrigin(upstream).origin
+    const upstreamOrigin = util.parseOrigin(upstream).origin
 
     const pool = this[kClients].find((pool) => (
       pool[kUrl].origin === upstreamOrigin &&
@@ -141,7 +144,7 @@ class BalancedPool extends PoolBase {
   }
 
   getUpstream (upstream) {
-    const upstreamOrigin = parseOrigin(upstream).origin
+    const upstreamOrigin = util.parseOrigin(upstream).origin
 
     return this[kClients].find((pool) => (
       pool[kUrl].origin === upstreamOrigin &&
diff --git a/test/node-test/balanced-pool.js b/test/node-test/balanced-pool.js
@@ -601,3 +601,39 @@ describe('weighted round robin', () => {
     })
   }
 })
+
+test('should not be vulnerable to __proto__ pollution via options', async (t) => {
+  const { EventEmitter } = require('node:events')
+
+  let capturedOpts
+
+  // Simulate attacker-controlled options with __proto__ property
+  const attackerOptions = JSON.parse(`
+    {
+      "__proto__": {
+        "polluted": "YES",
+        "connections": 1
+      }
+    }
+  `)
+
+  attackerOptions.factory = (origin, opts) => {
+    capturedOpts = opts
+
+    const stub = new EventEmitter()
+    stub.dispatch = () => true
+    stub.close = () => Promise.resolve()
+    stub.destroy = () => Promise.resolve()
+    stub.destroyed = false
+    stub.closed = false
+
+    return stub
+  }
+
+  new BalancedPool(['http://localhost/'], attackerOptions) // eslint-disable-line no-new
+
+  // Verify that the captured options do not have polluted prototype
+  assert.strictEqual(capturedOpts.polluted, undefined, 'polluted property should not exist on options')
+  assert.strictEqual(Object.getPrototypeOf(capturedOpts).polluted, undefined, 'prototype should not be polluted')
+  assert.strictEqual({}.polluted, undefined, 'global Object.prototype should not be polluted')
+})
