From 2d5971c88482d010af2dc14d4fc1c254dfee3284 Mon Sep 17 00:00:00 2001
From: kilisamemarisaaa <1798456934@qq.com>
Date: Mon, 31 Aug 2026 12:30:28 +0800
Subject: [PATCH 1/2] fix: ignore epilogue after multipart parser finish

---
 lib/types/multipart.js                |  5 ++++
 test/types-multipart-coverage.test.js | 36 +++++++++++++++++++++++++++
 2 files changed, 41 insertions(+)

diff --git a/lib/types/multipart.js b/lib/types/multipart.js
index 401f8af..7f23fe1 100644
--- a/lib/types/multipart.js
+++ b/lib/types/multipart.js
@@ -272,6 +272,11 @@ function Multipart (boy, cfg) {
 }
 
 Multipart.prototype.write = function (chunk, cb) {
+  if (!this.parser.writable) {
+    cb()
+    return
+  }
+
   const r = this.parser.write(chunk)
   if (r && !this._pause) {
     cb()
diff --git a/test/types-multipart-coverage.test.js b/test/types-multipart-coverage.test.js
index 6ea0f3d..478ff61 100644
--- a/test/types-multipart-coverage.test.js
+++ b/test/types-multipart-coverage.test.js
@@ -49,6 +49,42 @@ test('multipart parser accepts prototype property names', async (t) => {
   }
 })
 
+test('multipart parser ignores an epilogue written after the closing boundary', { timeout: 1000 }, async (t) => {
+  const boundary = 'epilogueboundary'
+  const body = buildBody([[
+    'Content-Disposition: form-data; name="field"',
+    '',
+    'value'
+  ]], boundary)
+  const busboy = new Busboy({
+    headers: { 'content-type': 'multipart/form-data; boundary=' + boundary }
+  })
+  const fields = []
+  let finishes = 0
+  busboy.on('field', (key, value) => fields.push([key, value]))
+  const finished = new Promise((resolve, reject) => {
+    busboy.once('error', reject)
+    busboy.once('finish', () => {
+      finishes++
+      resolve()
+    })
+  })
+
+  busboy.write(Buffer.from(body, 'utf8'))
+  await new Promise(resolve => setImmediate(resolve))
+  await new Promise((resolve, reject) => {
+    busboy.write(Buffer.from('epilogue', 'utf8'), error => {
+      if (error) reject(error)
+      else resolve()
+    })
+  })
+  busboy.end()
+
+  await finished
+  t.assert.deepStrictEqual(fields, [['field', 'value']])
+  t.assert.strictEqual(finishes, 1)
+})
+
 test('multipart parser rejects bare CR or LF in disposition parameters', async (t) => {
   const boundary = 'barecrlf'
   const dispositionValues = [

From 79db1682ea27333c422c266c81ad54234dbe1cf6 Mon Sep 17 00:00:00 2001
From: kilisamemarisaaa <1798456934@qq.com>
Date: Mon, 31 Aug 2026 12:56:54 +0800
Subject: [PATCH 2/2] fix: recognize epilogue by closing boundary

---
 lib/types/multipart.js                |  2 +-
 test/types-multipart-coverage.test.js | 16 +++++++++++++---
 2 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/lib/types/multipart.js b/lib/types/multipart.js
index 7f23fe1..5544f6e 100644
--- a/lib/types/multipart.js
+++ b/lib/types/multipart.js
@@ -272,7 +272,7 @@ function Multipart (boy, cfg) {
 }
 
 Multipart.prototype.write = function (chunk, cb) {
-  if (!this.parser.writable) {
+  if (this.parser._finished) {
     cb()
     return
   }
diff --git a/test/types-multipart-coverage.test.js b/test/types-multipart-coverage.test.js
index 478ff61..1c0e77e 100644
--- a/test/types-multipart-coverage.test.js
+++ b/test/types-multipart-coverage.test.js
@@ -59,12 +59,17 @@ test('multipart parser ignores an epilogue written after the closing boundary',
   const busboy = new Busboy({
     headers: { 'content-type': 'multipart/form-data; boundary=' + boundary }
   })
+  const events = []
   const fields = []
   let finishes = 0
-  busboy.on('field', (key, value) => fields.push([key, value]))
+  busboy.on('field', (key, value) => {
+    events.push('field')
+    fields.push([key, value])
+  })
   const finished = new Promise((resolve, reject) => {
     busboy.once('error', reject)
-    busboy.once('finish', () => {
+    busboy.on('finish', () => {
+      events.push('finish')
       finishes++
       resolve()
     })
@@ -75,13 +80,18 @@ test('multipart parser ignores an epilogue written after the closing boundary',
   await new Promise((resolve, reject) => {
     busboy.write(Buffer.from('epilogue', 'utf8'), error => {
       if (error) reject(error)
-      else resolve()
+      else {
+        events.push('epilogue write')
+        resolve()
+      }
     })
   })
   busboy.end()
 
   await finished
+  await new Promise(resolve => setImmediate(resolve))
   t.assert.deepStrictEqual(fields, [['field', 'value']])
+  t.assert.deepStrictEqual(events, ['field', 'epilogue write', 'finish'])
   t.assert.strictEqual(finishes, 1)
 })