From b2a693cefc6dde2fd09377a976005c562f0e745a Mon Sep 17 00:00:00 2001
From: Matteo Collina <hello@matteocollina.com>
Date: Wed, 2 Sep 2026 17:17:37 +0000
Subject: [PATCH] fix(proxy-agent): guard Proxy-Authorization in iterable
 header containers

buildHeaders() only materialized arrays, so a Map or Headers carrying
proxy-authorization passed through untouched and bypassed
throwIfProxyAuthIsSent(), whose Object.keys/for...in scan sees no entries
on those containers. The header was then forwarded through the CONNECT
tunnel to the origin, disclosing proxy credentials (GHSA-6cv7-626c-qhqw).

Materialize any iterable header container into a record in buildHeaders()
before the guard runs, and add regression tests for Map and Headers inputs.
---
 lib/dispatcher/proxy-agent.js | 16 ++++++++++++++++
 test/proxy-agent.js           | 27 +++++++++++++++++++++++++--
 2 files changed, 41 insertions(+), 2 deletions(-)

diff --git a/lib/dispatcher/proxy-agent.js b/lib/dispatcher/proxy-agent.js
index fd4577c1119..2b118581eec 100644
--- a/lib/dispatcher/proxy-agent.js
+++ b/lib/dispatcher/proxy-agent.js
@@ -9,6 +9,7 @@ const buildConnector = require('../core/connect')
 const Client = require('./client')
 const { channels } = require('../core/diagnostics')
 const Socks5ProxyAgent = require('./socks5-proxy-agent')
+const { hasSafeIterator } = require('../core/util')
 
 const kAgent = Symbol('proxy agent')
 const kClient = Symbol('proxy client')
@@ -345,6 +346,21 @@ function buildHeaders (headers) {
     return headersPair
   }
 
+  // Materialize iterable header containers (e.g. Map, Headers) into a record so
+  // that throwIfProxyAuthIsSent() can inspect their entries. Object.keys and
+  // for...in see nothing on a Map/Headers instance, so without this the
+  // Proxy-Authorization guard is bypassed and proxy credentials can reach the
+  // origin server (GHSA-6cv7-626c-qhqw).
+  if (headers && typeof headers === 'object' && hasSafeIterator(headers)) {
+    const headersPair = {}
+
+    for (const [key, value] of headers) {
+      headersPair[key] = value
+    }
+
+    return headersPair
+  }
+
   return headers
 }
 
diff --git a/test/proxy-agent.js b/test/proxy-agent.js
index c4d04b08d09..4d7e1d686b2 100644
--- a/test/proxy-agent.js
+++ b/test/proxy-agent.js
@@ -3,7 +3,7 @@
 const { tspl } = require('@matteo.collina/tspl')
 const { test, after } = require('node:test')
 const diagnosticsChannel = require('node:diagnostics_channel')
-const { request, fetch, setGlobalDispatcher, getGlobalDispatcher } = require('..')
+const { request, fetch, Headers, setGlobalDispatcher, getGlobalDispatcher } = require('..')
 const { InvalidArgumentError, ConnectTimeoutError, SecureProxyConnectionError } = require('../lib/core/errors')
 const ProxyAgent = require('../lib/dispatcher/proxy-agent')
 const Pool = require('../lib/dispatcher/pool')
@@ -837,7 +837,7 @@ test('use proxy-agent with custom headers with tunneling enabled', async (t) =>
 })
 
 test('sending proxy-authorization in request headers should throw', async (t) => {
-  t = tspl(t, { plan: 3 })
+  t = tspl(t, { plan: 5 })
   const server = await buildServer()
   const proxy = await buildProxy()
 
@@ -888,6 +888,29 @@ test('sending proxy-authorization in request headers should throw', async (t) =>
     'Proxy-Authorization should be sent in ProxyAgent'
   )
 
+  // Iterable containers (Map/Headers) must not bypass the guard (GHSA-6cv7-626c-qhqw)
+  await t.rejects(
+    request(
+      serverUrl + '/hello?foo=bar',
+      {
+        dispatcher: proxyAgent,
+        headers: new Map([['proxy-authorization', Buffer.from('user:pass').toString('base64')]])
+      }
+    ),
+    'Proxy-Authorization should be sent in ProxyAgent'
+  )
+
+  await t.rejects(
+    request(
+      serverUrl + '/hello?foo=bar',
+      {
+        dispatcher: proxyAgent,
+        headers: new Headers({ 'proxy-authorization': Buffer.from('user:pass').toString('base64') })
+      }
+    ),
+    'Proxy-Authorization should be sent in ProxyAgent'
+  )
+
   server.close()
   proxy.close()
   proxyAgent.close()