commit 5a8d121a1f3ef5ad7c105ee378cc79a3eac0c7d4
author Rishi <rishi_devan@mail.com> Wed Jul 15 13:51:00 2020 +0200
committer GitHub <noreply@github.com> Wed Jul 15 13:51:00 2020 +0200
tree 68dffaf58d9509ec482ef1cddd0815fbd5c70fa7
parent bbceef6851895135c80e588a55854c1afab46499

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

diff --git a/Lib/tarfile.py b/Lib/tarfile.py
index e2b6053..6769066 100755
--- a/Lib/tarfile.py
+++ b/Lib/tarfile.py
@@ -1249,6 +1249,8 @@
 
             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"