2 files changed, 8 insertions, 0 deletions
diff --git a/Lib/smtplib.py b/Lib/smtplib.py
index 47569738f0..dfbf5f9324 100755
--- a/Lib/smtplib.py
+++ b/Lib/smtplib.py
@@ -773,6 +773,11 @@ class SMTP:
             self.ehlo_resp = None
             self.esmtp_features = {}
             self.does_esmtp = 0
+        else:
+            # RFC 3207:
+            # 501 Syntax error (no parameters allowed)
+            # 454 TLS not available due to temporary reason
+            raise SMTPResponseException(resp, reply)
         return (resp, reply)
 
     def sendmail(self, from_addr, to_addrs, msg, mail_options=[],
diff --git a/Misc/NEWS b/Misc/NEWS
index cc5ba7de83..418fd5c1bc 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -139,6 +139,9 @@ Core and Builtins
 Library
 -------
 
+- Fix TLS stripping vulnerability in smptlib, CVE-2016-0772.  Reported by Team
+  Oststrom
+
 - Issue #21386: Implement missing IPv4Address.is_global property.  It was
   documented since 07a5610bae9d.  Initial patch by Roger Luethi.