commit aa7b03b31bf09b21a012b24e21977538e66b0172
author Miss Skeleton (bot) <31488909+miss-islington@users.noreply.github.com> Tue Oct 20 00:17:22 2020 -0700
committer GitHub <noreply@github.com> Tue Oct 20 09:17:22 2020 +0200
tree 6cbf49560820ab3c37a04cfcfd9d9a26f0bebe64
parent 479553c7c11306a09ce34edb6ef208133b7b95fe

bpo-41471: Ignore invalid prefix lengths in system proxy settings on macOS (GH-22762) (GH-22773)

(cherry picked from commit 93a1ccabdede416425473329b8c718d507c55e29)

Co-authored-by: Ronald Oussoren <ronaldoussoren@mac.com>

Lib/urllib/request.py

diff --git a/Lib/urllib/request.py b/Lib/urllib/request.py
index 2a3d715..a8c870b 100644
--- a/Lib/urllib/request.py
+++ b/Lib/urllib/request.py
@@ -2596,6 +2596,11 @@
                 mask = 8 * (m.group(1).count('.') + 1)
             else:
                 mask = int(mask[1:])
+
+            if mask < 0 or mask > 32:
+                # System libraries ignore invalid prefix lengths
+                continue
+
             mask = 32 - mask
 
             if (hostIP >> mask) == (base >> mask):