From 9282a06c8e1e298c20b3111867c8b28a93e389f5 Mon Sep 17 00:00:00 2001
From: Marcus Bointon <marcus@synchromedia.co.uk>
Date: Sun, 20 Oct 2019 20:49:36 +0200
Subject: [PATCH] Use shorter hashes for CID values, see #1691

---
 src/PHPMailer.php | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/PHPMailer.php b/src/PHPMailer.php
index 21e9df1a..9e857724 100644
--- a/src/PHPMailer.php
+++ b/src/PHPMailer.php
@@ -4022,7 +4022,8 @@ class PHPMailer
                     if ('.' === $directory) {
                         $directory = '';
                     }
-                    $cid = hash('sha256', $url) . '@phpmailer.0'; // RFC2392 S 2
+                    // RFC2392 S 2
+                    $cid = substr(hash('sha256', $data), 0, 32) . '@phpmailer.0';
                     if (strlen($basedir) > 1 && '/' !== substr($basedir, -1)) {
                         $basedir .= '/';
                     }