SourceTree for Windows Security Advisory 24th March 2021

SourceTree for Windows - Remote Code Injection using Git LFS - CVE-2020-27955 & CVE-2021-21237

Summary of Vulnerability

This advisory discloses a critical severity security vulnerability which wasintroduced through the git-lfs library and discovered in version 3.3.9 of SourceTree for Windows. Both CVE-2020-27955 & CVE-2021-21237 refer to the same underlying vulnerability, Remote Code Injection using Git LFS. Versions of SourceTree for Windows starting with 0.9.4 before 3.4.3 (the fixed version for CVE-2020-27955 and CVE-2021-21237) are affected by this vulnerability.

Remote Code Injection using Git LFS - CVE-2020-27955 & CVE-2021-21237

Severity

Atlassian rates the severity level of this vulnerability as critical, according to the scale published in our Atlassian severity levels. The scale allows us to rank the severity as critical, high, moderate or low.

This is our assessment and you should evaluate its applicability to your own IT environment.

Description

Vulnerability occurs when a user clones a malicious repository and tries to enable Git LFS to the repository

1. Clone the repository

2. Go to the Repository Tab -> Git LFS -> Start Repo

Loading a malicious repository will allow an attacker to execute arbitrary commands on the system.

All versions of SourceTree for Windows up to and including 3.4.2 are affected by this vulnerability.

This issue can be tracked here:

• SRCTREEWIN-13410 - RCE via git-lfs in Sourcetree for Windows - CVE-2020-27955 - CLOSED

• SRCTREEWIN-13480 - RCE via git-lfs in Sourcetree for Windows - CVE-2021-21237 - CLOSED

Vulnerability References

• CVE-2020-27955 advisory from Github: https://github.com/git-lfs/git-lfs/security/advisories/GHSA-4g4p-42wc-9f3m

• CVE-2021-21237 advisory from Github: https://github.com/git-lfs/git-lfs/security/advisories/GHSA-cx3w-xqmc-84g5

• Original advisory by Dawid Golunski: https://legalhackers.com/advisories/Git-LFS-RCE-Exploit-CVE-2020-27955.html

Fix

We have taken the following steps to address this issue:

1. Released version 3.4.3 that contains a fix for this issue.

What You Need to Do

Atlassian recommends that you upgrade to the latest version. For a full description of the latest version of SourceTree for Windows, see the release notes. Download the latest version of the standard installer or the enterprise installer.

Upgrade to version 3.4.3 or higher.

Mitigation

• Update git and git-lfs on your system to the latest versions and use them in your existing Sourcetree.

Support

If you did not receive an email for this advisory and you wish to receive such emails in the future go to https://my.atlassian.com/email and subscribe to Alerts emails.

If you have questions or concerns regarding this advisory, please raise a support request at https://support.atlassian.com/.

References