Bamboo Security Advisory 2021-04-07
CVE-2020-27955 & CVE-2021-21237 - Remote Code Injection using Git LFS
Advisory Release Date
Apr 7, 2021 10:00 AM PDT (Pacific Time, -7 hours)
Bamboo elastic agent AMI for Windows
Summary of Vulnerability
This advisory discloses a critical severity security vulnerability which was introduced through the git-lfs library and discovered in Stock Elastic Windows Images shipped with version 7.2.2 of Bamboo for Windows. Both CVE-2020-27955 & CVE-2021-21237 refer to the same underlying vulnerability, Remote Code Injection using Git LFS. Bamboo Stock Elastic Windows Images shipped with versions of Bamboo for Windows before 7.2.3 (the fixed version for CVE-2020-27955 & CVE-2021-21237) are affected by this vulnerability.
Customers using the Bamboo Windows elastic agent AMI on version 7.2.3 are not affected.
Customers using Bamboo for any non-Windows OS are not affected.
Customers using the Bamboo Windows elastic agent AMI on version 7.2.2 or earlier
Please upgrade your installations immediately to fix this vulnerability.
Customers using Bamboo for Windows
Ensure that git-lfs is updated to avoid being vulnerable. Refer to the advisories from Git, linked in “Vulnerability References”.
Remote Code Injection using Git LFS - CVE-2020-27955 & CVE-2021-21237
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.
The vulnerability occurs if git-lfs operates on a malicious repository with a git.bat or git.exe file in the current directory, allowing an attacker to execute arbitrary code.
run Git LFS on a on a malicious repository with a git.bat or git.exe file in the current directory
All versions of Bamboo for Windows up to and including 7.2.2 are affected by this vulnerability. This issue can be tracked here:
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
We have taken the following steps to address this issue:
Released Bamboo for Windows version 7.2.3 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 Bamboo for Windows, see the release note You can download the latest version of Bamboo for Windows from the download centre.
Upgrade Bamboo for Windows to version 7.2.3 or higher and update git-lfs on Windows
Customers using Bamboo for Windows need to update git-lfs on Windows to the latest version
Customers using Bamboo elastic agent AMI: Upgrade Bamboo for Windows to version 7.2.3
Update git and git-lfs on your system to the latest versions and use them in your existing Bamboo instance.
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As per our new policy critical security bug fixes will be back ported in accordance with https://www.atlassian.com/trust/security/bug-fix-policy. We will release new maintenance releases for the versions covered by the policy instead of binary patches.
Binary patches are no longer released.
Atlassian security advisories include a severity level and a CVE identifier. This severity level is based on our self-calculated CVSS score for each specific vulnerability. CVSS is an industry standard vulnerability metric. You can also learn more about CVSS at FIRST.org.