#17369: Improve handling of broken RFC2231 values in get_filename.

This fixes a regression relative to python2.

1 files changed, 4 insertions, 0 deletions

diff --git a/Lib/email/utils.py b/Lib/email/utils.py
index 93a625c8b4..f76c21eb1b 100644
--- a/Lib/email/utils.py
+++ b/Lib/email/utils.py
@@ -337,6 +337,10 @@ def collapse_rfc2231_value(value, errors='replace',
     # object.  We do not want bytes() normal utf-8 decoder, we want a straight
     # interpretation of the string as character bytes.
     charset, language, text = value
+    if charset is None:
+        # Issue 17369: if charset/lang is None, decode_rfc2231 couldn't parse
+        # the value, so use the fallback_charset.
+        charset = fallback_charset
     rawbytes = bytes(text, 'raw-unicode-escape')
     try:
         return str(rawbytes, charset, errors)