From 5a8d121a1f3ef5ad7c105ee378cc79a3eac0c7d4 Mon Sep 17 00:00:00 2001
From: Rishi <rishi_devan@mail.com>
Date: Wed, 15 Jul 2020 13:51:00 +0200
Subject: [PATCH] bpo-39017: Avoid infinite loop in the tarfile module
 (GH-21454)

Avoid infinite loop when reading specially crafted TAR files using the tarfile module
(CVE-2019-20907).
---
 Lib/tarfile.py                                    |   2 ++

diff --git a/Lib/tarfile.py b/Lib/tarfile.py
index e2b60532f6..6769066cab 100755
--- a/Lib/tarfile.py
+++ b/Lib/tarfile.py
@@ -1249,6 +1249,8 @@ class TarInfo(object):
 
             length, keyword = match.groups()
             length = int(length)
+            if length == 0:
+                raise InvalidHeaderError("invalid header")
             value = buf[match.end(2) + 1:match.start(1) + length - 1]
 
             # Normally, we could just use "utf-8" as the encoding and "strict"