From 542756f66732dfd4579c71951830a0b39ba05d57 Mon Sep 17 00:00:00 2001
From: Oubaida <oubaidaauau878@gmail.com>
Date: Fri, 7 Aug 2026 23:43:20 +0300
Subject: [PATCH] fix: support raw ArrayBuffer in res.send (#7362)

---
 lib/response.js  | 10 +++++++++-
 test/res.send.js | 26 +++++++++++++++++---------
 2 files changed, 26 insertions(+), 10 deletions(-)

diff --git a/lib/response.js b/lib/response.js
index b4755a5c060..da63b8c0fad 100644
--- a/lib/response.js
+++ b/lib/response.js
@@ -146,12 +146,16 @@ res.send = function send(body) {
     case 'boolean':
     case 'number':
     case 'object':
+
       if (chunk === null) {
         chunk = '';
-      } else if (ArrayBuffer.isView(chunk)) {
+      } else if (ArrayBuffer.isView(chunk) || chunk instanceof ArrayBuffer) {
         if (!this.get('Content-Type')) {
           this.type('bin');
         }
+        if (chunk instanceof ArrayBuffer) {
+          chunk = Buffer.from(chunk);
+        }
       } else {
         return this.json(chunk);
       }
@@ -166,9 +170,13 @@ res.send = function send(body) {
   // Content-Length should be added only if there is no Transfer-Encoding header
   var len;
   if (chunk !== undefined && !this.get('Transfer-Encoding')) {
+
     if (Buffer.isBuffer(chunk)) {
       // get length of Buffer
       len = chunk.length
+    } else if (ArrayBuffer.isView(chunk)) {
+      // get length of ArrayBuffer
+      len = chunk.byteLength
     } else if (!generateETag && chunk.length < 1000) {
       // just calculate length when no ETag + small chunk
       len = Buffer.byteLength(chunk, encoding)
diff --git a/test/res.send.js b/test/res.send.js
index f38ffde9776..1d9beea3a9b 100644
--- a/test/res.send.js
+++ b/test/res.send.js
@@ -165,11 +165,9 @@ describe('res', function(){
   describe('.send(Buffer)', function(){
     it('should send as octet-stream', function(done){
       var app = express();
-
       app.use(function(req, res){
         res.send(Buffer.from('hello'))
       });
-
       request(app)
         .get('/')
         .expect(200)
@@ -180,11 +178,9 @@ describe('res', function(){
 
     it('should set ETag', function (done) {
       var app = express();
-
       app.use(function (req, res) {
         res.send(Buffer.alloc(999, '-'))
       });
-
       request(app)
       .get('/')
       .expect('ETag', 'W/"3e7-qPnkJ3CVdVhFJQvUBfF10TmVA7g"')
@@ -193,11 +189,9 @@ describe('res', function(){
 
     it('should not override Content-Type', function(done){
       var app = express();
-
       app.use(function(req, res){
         res.set('Content-Type', 'text/plain').send(Buffer.from('hey'))
       });
-
       request(app)
       .get('/')
       .expect('Content-Type', 'text/plain; charset=utf-8')
@@ -210,20 +204,34 @@ describe('res', function(){
         const encodedHey = new TextEncoder().encode("hey");
         res.set("Content-Type", "text/plain").send(encodedHey);
       })
-
       request(app)
         .get("/")
         .expect("Content-Type", "text/plain; charset=utf-8")
         .expect(200, "hey", done);
     })
 
+    it('should handle a raw ArrayBuffer as binary data, not JSON', function(done){
+      var app = express();
+      app.use(function(req, res){
+        const arrayBuffer = new ArrayBuffer(3);
+        const view = new Uint8Array(arrayBuffer);
+        view.set([10, 20, 30]);
+        res.send(arrayBuffer);
+      });
+      request(app)
+        .get('/')
+        .expect(200)
+        .expect('Content-Type', 'application/octet-stream')
+        .expect(utils.shouldHaveBody(Buffer.from([10, 20, 30])))
+        .expect('Content-Length', "3")
+        .end(done);
+    })
+
     it('should not override ETag', function (done) {
       var app = express()
-
       app.use(function (req, res) {
         res.type('text/plain').set('ETag', '"foo"').send(Buffer.from('hey'))
       })
-
       request(app)
       .get('/')
       .expect('ETag', '"foo"')