[ASA-202103-3] git: arbitrary code execution

[Morten Linderud]

Arch Linux Security Advisory ASA-202103-3
=========================================

Severity: Low
Date    : 2021-03-13
CVE-ID  : CVE-2021-21300
Package : git
Type    : arbitrary code execution
Remote  : Yes
Link    : https://security.archlinux.org/AVG-1665

Summary
=======

The package git before version 2.30.2-1 is vulnerable to arbitrary code
execution.

Resolution
==========

Upgrade to 2.30.2-1.

# pacman -Syu "git>=2.30.2-1"

The problem has been fixed upstream in version 2.30.2.

Workaround
==========

None.

Description
===========

In affected versions of Git a specially crafted repository that
contains symbolic links as well as files using a clean/smudge filter
such as Git LFS, may cause just-checked out script to be executed while
cloning onto a case-insensitive file system such as NTFS, HFS+ or APFS.
Note that clean/smudge filters have to be configured for that. As a
workaround, if symbolic link support is disabled in Git (e.g. via `git
config --global core.symlinks false`), the described attack won't work.
Likewise, if no clean/smudge filters such as Git LFS are configured
globally (i.e. _before_ cloning), the attack is foiled. As always, it
is best to avoid cloning repositories from untrusted sources. The
earliest impacted version is 2.14.2. The fix versions are: 2.30.1,
2.29.3, 2.28.1, 2.27.1, 2.26.3, 2.25.5, 2.24.4, 2.23.4, 2.22.5, 2.21.4,
2.20.5, 2.19.6, 2.18.5, 2.17.62.17.6.

Impact
======

Under certain circumstances, a remote attacker might be able to execute
arbitrary code by getting a local user to clone a crafted repository.

References
==========

https://github.com/git/git/security/advisories/GHSA-8prw-h3cq-mghm
https://lore.kernel.org/git/xmqqim6019yd.fsf@gitster.c.googlers.com/
https://git.kernel.org/pub/scm/git/git.git/commit/?id=684dd4c2b414bcf648505e74498a608f28de4592
https://security.archlinux.org/CVE-2021-21300
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