From 19f72110fc448e58dcd2d867d1db1fc547b790f2 Mon Sep 17 00:00:00 2001
From: Lars Ingebrigtsen <larsi@gnus.org>
Date: Sun, 20 Oct 2019 09:40:11 +0200
Subject: [PATCH] Protect against invalid punycode

* lisp/net/puny.el (puny-decode-string): Protect against invalid
punycode.
---
 lisp/net/puny.el | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/lisp/net/puny.el b/lisp/net/puny.el
index 23c7af80619..729076ddbd7 100644
--- a/lisp/net/puny.el
+++ b/lisp/net/puny.el
@@ -63,7 +63,10 @@ For instance, \"xn--ff-2sa.org\" => \"fśf.org\"."
   "Decode an IDNA/punycode-encoded string.
 For instance \"xn--bcher-kva\" => \"bücher\"."
   (if (string-match "\\`xn--" string)
-      (puny-decode-string-internal (substring string 4))
+      (condition-case nil
+          (puny-decode-string-internal (substring string 4))
+        ;; If the string is invalid Punycode, just return the string.
+        (args-out-of-range string))
     string))
 
 (defconst puny-initial-n 128)
-- 
2.39.2