[12.x] Fix embedded image Content-ID inconsistency in cloned emails

src/Illuminate/Mail/Message.php

@@ -4,7 +4,6 @@
 
 use Illuminate\Contracts\Mail\Attachable;
 use Illuminate\Support\Collection;
-use Illuminate\Support\Str;
 use Illuminate\Support\Traits\ForwardsCalls;
 use Symfony\Component\Mime\Address;
 use Symfony\Component\Mime\Email;
@@ -344,31 +343,27 @@ public function embed($file)
         if ($file instanceof Attachment) {
             return $file->attachWith(
                 function ($path) use ($file) {
-                    $cid = $file->as ?? Str::random();
+                    $part = (new DataPart(new File($path), $file->as, $file->mime))->asInline();
 
-                    $this->message->addPart(
-                        (new DataPart(new File($path), $cid, $file->mime))->asInline()
-                    );
+                    $this->message->addPart($part);
 
-                    return "cid:{$cid}";
+                    return "cid:{$part->getContentId()}";
                 },
                 function ($data) use ($file) {
-                    $this->message->addPart(
-                        (new DataPart($data(), $file->as, $file->mime))->asInline()
-                    );
+                    $part = (new DataPart($data(), $file->as, $file->mime))->asInline();
+                    $this->message->addPart($part);
 
-                    return "cid:{$file->as}";
+                    return "cid:{$part->getContentId()}";
                 }
             );
         }
 
-        $cid = Str::random(10);
+        $fileObject = new File($file);
+        $part = (new DataPart($fileObject, $fileObject->getFilename()))->asInline();
 
-        $this->message->addPart(
-            (new DataPart(new File($file), $cid))->asInline()
-        );
+        $this->message->addPart($part);
 
-        return "cid:$cid";
+        return "cid:{$part->getContentId()}";
     }
 
     /**
@@ -381,11 +376,11 @@ function ($data) use ($file) {
      */
     public function embedData($data, $name, $contentType = null)
     {
-        $this->message->addPart(
-            (new DataPart($data, $name, $contentType))->asInline()
-        );
+        $part = (new DataPart($data, $name, $contentType))->asInline();
+
+        $this->message->addPart($part);
 
-        return "cid:$name";
+        return "cid:{$part->getContentId()}";
     }
 
     /**

tests/Integration/Mail/Fixtures/embed-image.blade.php

@@ -0,0 +1 @@
+Embedded image: <img src="{{ $message->embed($image) }}" alt="Embedded test image" />

tests/Integration/Mail/Fixtures/embed.blade.php

@@ -1 +1,3 @@
+Embed file: {{ basename(__FILE__) }}
+
 Embed content: {{ $message->embed(__FILE__) }}

tests/Integration/Mail/SendingMarkdownMailTest.php

@@ -52,23 +52,28 @@ public function testEmbed()
         $email = app('mailer')->getSymfonyTransport()->messages()[0]->getOriginalMessage()->toString();
 
         $cid = explode(' cid:', (new Stringable($email))->explode("\r\n")
-            ->filter(fn ($line) => str_contains($line, 'Embed content: cid:'))
+            ->filter(fn ($line) => str_contains($line, ' content: cid:'))
+            ->first())[1];
+
+        $filename = explode('Embed file: ', (new Stringable($email))->explode("\r\n")
+            ->filter(fn ($line) => str_contains($line, ' file:'))
             ->first())[1];
 
         $this->assertStringContainsString(<<<EOT
-        Content-Type: application/x-php; name=$cid\r
+        Content-Type: application/x-php; name=$filename\r
         Content-Transfer-Encoding: base64\r
-        Content-Disposition: inline; name=$cid; filename=$cid\r
+        Content-Disposition: inline; name=$filename;\r
+         filename=$filename\r
+        Content-ID: <$cid>\r
         EOT, $email);
     }
 
     public function testEmbedData()
     {
         Mail::to('test@mail.com')->send($mailable = new EmbedDataMailable());
 
-        $mailable->assertSeeInHtml('Embed data content: cid:foo.jpg');
         $mailable->assertSeeInText('Embed data content: ');
-        $mailable->assertDontSeeInText('Embed data content: cid:foo.jpg');
+        $mailable->assertSeeInHtml('Embed data content: cid:');
 
         $email = app('mailer')->getSymfonyTransport()->messages()[0]->getOriginalMessage()->toString();
 
@@ -87,8 +92,7 @@ public function testEmbedMultilineImage()
 
         $this->assertStringContainsString('Embed multiline content: <img', $html);
         $this->assertStringContainsString('alt="multiline image"', $html);
-        $this->assertStringContainsString('data:image/png;base64', $html);
-        $this->assertStringNotContainsString('cid:foo.jpg', $html);
+        $this->assertStringContainsString('<img src="cid:', $html);
     }
 
     public function testMessageAsPublicPropertyMayBeDefinedAsViewData()
@@ -128,6 +132,49 @@ public function testTheme()
         Mail::to('test@mail.com')->send(new BasicMailable());
         $this->assertSame('default', app(Markdown::class)->getTheme());
     }
+
+    public function testEmbeddedImageContentIdConsistencyAcrossMailerFailoverClones()
+    {
+        Mail::to('test@mail.com')->send($mailable = new EmbedImageMailable);
+
+        /** @var \Symfony\Component\Mime\Email $originalEmail */
+        $originalEmail = app('mailer')->getSymfonyTransport()->messages()[0]->getOriginalMessage();
+        $expectedContentId = $originalEmail->getAttachments()[0]->getContentId();
+
+        // Simulate failover mailer scenario where email is cloned for retry.
+        // After shallow clone, the CID in HTML and attachment Content-ID header should remain consistent.
+        $firstClonedEmail = quoted_printable_decode((clone $originalEmail)->toString());
+        [$htmlCid, $attachmentContentId] = $this->extractContentIdsFromEmail($firstClonedEmail);
+
+        $this->assertEquals($htmlCid, $attachmentContentId, 'HTML img src CID should match attachment Content-ID header');
+        $this->assertEquals($expectedContentId, $htmlCid, 'Cloned email CID should match original attachment CID');
+
+        // Verify consistency is maintained across multiple clone operations (e.g., multiple retries).
+        $secondClonedEmail = quoted_printable_decode((clone $originalEmail)->toString());
+        [$htmlCid, $attachmentContentId] = $this->extractContentIdsFromEmail($secondClonedEmail);
+
+        $this->assertEquals($htmlCid, $attachmentContentId, 'HTML img src CID should match attachment Content-ID header on subsequent clone');
+        $this->assertEquals($expectedContentId, $htmlCid, 'Multiple clones should preserve original CID');
+    }
+
+    /**
+     * Extract Content IDs from email for embedded image validation.
+     *
+     * @param  string  $rawEmail
+     * @return array{0: string|null, 1: string|null} [HTML image CID, attachment Content-ID]
+     */
+    private function extractContentIdsFromEmail(string $rawEmail): array
+    {
+        // Extract CID from HTML <img src="cid:..."> tag.
+        preg_match('/<img[^>]+src="cid:([^"]+)"/', $rawEmail, $htmlMatches);
+        $htmlImageCid = $htmlMatches[1] ?? null;
+
+        // Extract CID from MIME attachment Content-ID header.
+        preg_match('/Content-ID:\s*<([^>]+)>/', $rawEmail, $headerMatches);
+        $attachmentContentId = $headerMatches[1] ?? null;
+
+        return [$htmlImageCid, $attachmentContentId];
+    }
 }
 
 class BasicMailable extends Mailable
@@ -236,6 +283,26 @@ public function content()
     }
 }
 
+class EmbedImageMailable extends Mailable
+{
+    public function envelope()
+    {
+        return new Envelope(
+            subject: 'My basic title',
+        );
+    }
+
+    public function content()
+    {
+        return new Content(
+            markdown: 'embed-image',
+            with: [
+                'image' => __DIR__.DIRECTORY_SEPARATOR.'Fixtures'.DIRECTORY_SEPARATOR.'empty_image.jpg',
+            ]
+        );
+    }
+}
+
 class MessageAsPublicPropertyMailable extends Mailable
 {
     public $message = 'My message';

tests/Integration/Notifications/Fixtures/markdown.blade.php

@@ -1 +1,2 @@
+Embed file: {{ basename(__FILE__) }}
 Embed content: {{ $message->embed(__FILE__) }}

tests/Integration/Notifications/SendingMailableNotificationsTest.php

@@ -49,16 +49,24 @@ public function testMarkdownNotification()
 
         $user->notify(new MarkdownNotification());
 
-        $email = app('mailer')->getSymfonyTransport()->messages()[0]->getOriginalMessage()->toString();
+        $message = app('mailer')->getSymfonyTransport()->messages()[0]->getOriginalMessage();
+        $email = $message->toString();
+        $textBody = $message->getTextBody();
 
-        $cid = explode(' cid:', (new Stringable($email))->explode("\r\n")
+        $cid = explode(' cid:', (new Stringable($textBody))->explode("\n")
             ->filter(fn ($line) => str_contains($line, 'Embed content: cid:'))
             ->first())[1];
 
+        $filename = explode(' file: ', (new Stringable($textBody))->explode("\n")
+            ->filter(fn ($line) => str_contains($line, 'Embed file: '))
+            ->first())[1];
+
         $this->assertStringContainsString(<<<EOT
-        Content-Type: application/x-php; name=$cid\r
+        Content-Type: application/x-php; name=$filename\r
         Content-Transfer-Encoding: base64\r
-        Content-Disposition: inline; name=$cid; filename=$cid\r
+        Content-Disposition: inline; name=$filename;\r
+         filename=$filename\r
+        Content-ID: <$cid>\r
         EOT, $email);
     }
 

tests/Mail/MailMessageTest.php

@@ -165,13 +165,14 @@ public function testEmbedPath(): void
         $cid = $this->message->embed($path);
 
         $this->assertStringStartsWith('cid:', $cid);
-        $name = Str::after($cid, 'cid:');
+        $contentId = Str::after($cid, 'cid:');
         $attachment = $this->message->getSymfonyMessage()->getAttachments()[0];
         $headers = $attachment->getPreparedHeaders()->toArray();
         $this->assertSame('bar', $attachment->getBody());
-        $this->assertSame("Content-Type: image/jpeg; name={$name}", $headers[0]);
+        $this->assertSame($contentId, $attachment->getContentId());
+        $this->assertStringContainsString('Content-Type: image/jpeg', $headers[0]);
         $this->assertSame('Content-Transfer-Encoding: base64', $headers[1]);
-        $this->assertSame("Content-Disposition: inline; name={$name}; filename={$name}", $headers[2]);
+        $this->assertStringContainsString('Content-Disposition: inline', $headers[2]);
 
         unlink($path);
     }
@@ -182,7 +183,9 @@ public function testDataEmbed(): void
 
         $attachment = $this->message->getSymfonyMessage()->getAttachments()[0];
         $headers = $attachment->getPreparedHeaders()->toArray();
-        $this->assertSame('cid:foo.jpg', $cid);
+        $this->assertStringStartsWith('cid:', $cid);
+        $contentId = Str::after($cid, 'cid:');
+        $this->assertSame($contentId, $attachment->getContentId());
         $this->assertSame('bar', $attachment->getBody());
         $this->assertSame('Content-Type: image/png; name=foo.jpg', $headers[0]);
         $this->assertSame('Content-Transfer-Encoding: base64', $headers[1]);
@@ -201,9 +204,11 @@ public function toMailAttachment()
             }
         });
 
-        $this->assertSame('cid:baz', $cid);
+        $this->assertStringStartsWith('cid:', $cid);
+        $contentId = Str::after($cid, 'cid:');
         $attachment = $this->message->getSymfonyMessage()->getAttachments()[0];
         $headers = $attachment->getPreparedHeaders()->toArray();
+        $this->assertSame($contentId, $attachment->getContentId());
         $this->assertSame('bar', $attachment->getBody());
         $this->assertSame('Content-Type: image/png; name=baz', $headers[0]);
         $this->assertSame('Content-Transfer-Encoding: base64', $headers[1]);
@@ -225,14 +230,14 @@ public function toMailAttachment()
         });
 
         $this->assertStringStartsWith('cid:', $cid);
-        $name = Str::after($cid, 'cid:');
-        $this->assertSame(16, mb_strlen($name));
+        $contentId = Str::after($cid, 'cid:');
         $attachment = $this->message->getSymfonyMessage()->getAttachments()[0];
+        $this->assertSame($contentId, $attachment->getContentId());
         $headers = $attachment->getPreparedHeaders()->toArray();
         $this->assertSame('bar', $attachment->getBody());
-        $this->assertSame("Content-Type: image/jpeg; name={$name}", $headers[0]);
+        $this->assertStringContainsString('Content-Type: image/jpeg', $headers[0]);
         $this->assertSame('Content-Transfer-Encoding: base64', $headers[1]);
-        $this->assertSame("Content-Disposition: inline; name={$name};\r\n filename={$name}", $headers[2]);
+        $this->assertStringContainsString('Content-Disposition: inline', $headers[2]);
 
         unlink($path);
     }