From 4875387ea44b46879574c81e73e55e24953ae254 Mon Sep 17 00:00:00 2001
From: Meghan Denny <meghan@bun.com>
Date: Sat, 22 Nov 2025 17:20:50 -0800
Subject: [PATCH] fix sending a header to the server more than once

---
 src/bun.js/bindings/NodeHTTP.cpp                | 17 +++++++++++++++--
 ...e-to-send-array-of-[key-value]-as-headers.ts |  1 -
 .../parallel/test-http-server-multiheaders.js   |  1 -
 3 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/src/bun.js/bindings/NodeHTTP.cpp b/src/bun.js/bindings/NodeHTTP.cpp
index 9f685fa555..f6b02368da 100644
--- a/src/bun.js/bindings/NodeHTTP.cpp
+++ b/src/bun.js/bindings/NodeHTTP.cpp
@@ -155,10 +155,12 @@ static void assignHeadersFromUWebSocketsForCall(uWS::HttpRequest* request, JSVal
         HTTPHeaderIdentifiers& identifiers = WebCore::clientData(vm)->httpHeaderIdentifiers();
         Identifier nameIdentifier;
         JSString* nameString = nullptr;
+        bool headerIsWellKnown = false;
 
         if (WebCore::findHTTPHeaderName(nameView, name)) {
             nameString = identifiers.stringFor(globalObject, name);
             nameIdentifier = identifiers.identifierFor(vm, name);
+            headerIsWellKnown = true;
         } else {
             WTF::String wtfString = nameView.toString();
             nameString = jsString(vm, wtfString);
@@ -177,13 +179,24 @@ static void assignHeadersFromUWebSocketsForCall(uWS::HttpRequest* request, JSVal
             arrayValues.append(jsValue);
             setCookiesHeaderArray->push(globalObject, jsValue);
             RETURN_IF_EXCEPTION(scope, void());
-
         } else {
+            if (headersObject->hasOwnProperty(globalObject, nameIdentifier)) {
+                if (headerIsWellKnown && name == HTTPHeaderName::Host) {
+                    continue;
+                }
+                auto prev = headersObject->get(globalObject, nameIdentifier);
+                RETURN_IF_EXCEPTION(scope, );
+                auto thenew = jsString(vm, makeString(prev.getString(globalObject), ", "_s, jsValue));
+                headersObject->putDirectMayBeIndex(globalObject, nameIdentifier, thenew);
+                RETURN_IF_EXCEPTION(scope, );
+                arrayValues.append(nameString);
+                arrayValues.append(jsValue);
+                continue;
+            }
             headersObject->putDirectMayBeIndex(globalObject, nameIdentifier, jsValue);
             RETURN_IF_EXCEPTION(scope, void());
             arrayValues.append(nameString);
             arrayValues.append(jsValue);
-            RETURN_IF_EXCEPTION(scope, void());
         }
     }
 
diff --git a/test/js/bun/test/parallel/test-http-client-should-be-able-to-send-array-of-[key-value]-as-headers.ts b/test/js/bun/test/parallel/test-http-client-should-be-able-to-send-array-of-[key-value]-as-headers.ts
index 9003dbd906..f637001012 100644
--- a/test/js/bun/test/parallel/test-http-client-should-be-able-to-send-array-of-[key-value]-as-headers.ts
+++ b/test/js/bun/test/parallel/test-http-client-should-be-able-to-send-array-of-[key-value]-as-headers.ts
@@ -3,7 +3,6 @@ import { once } from "node:events";
 import http from "node:http";
 import type { AddressInfo } from "node:net";
 const { expect } = createTest(import.meta.path);
-if ("Bun" in globalThis) process.exit(0); // TODO: BUN
 
 const { promise, resolve } = Promise.withResolvers();
 await using server = http.createServer((req, res) => {
diff --git a/test/js/node/test/parallel/test-http-server-multiheaders.js b/test/js/node/test/parallel/test-http-server-multiheaders.js
index bfd56d1231..8f633fdb99 100644
--- a/test/js/node/test/parallel/test-http-server-multiheaders.js
+++ b/test/js/node/test/parallel/test-http-server-multiheaders.js
@@ -25,7 +25,6 @@
 // that support it, and dropping duplicates for other fields.
 
 require('../common');
-if ('Bun' in globalThis) return; // TODO: BUN
 const assert = require('assert');
 const http = require('http');