GitHub has urged users to make “critical” Git project code updates after nine security vulnerabilities were found in the open source version-control system.
It is “especially critical” that Git on Windows users patch fast, GitHub said, with the flaws potentially allowing attackers to “overwrite arbitrary paths, remotely execute code, and/or overwrite files in the .git/ directory”.
The Git project was originally founded to support Linux kernel development. Git is a program that tracks changes made to files. Once installed, Git can be used to create repositories, or a.git/ folder inside a project. Git vulnerabilities in theory could be used to steal sensitive commercial IP, or to sabotage code.
The Git Project Vulnerabilities
Among the vulnerabilities was CVE-2019-1350, which through incorrect quoting of command-line arguments allows remote code execution during a recursive clone in conjunction with SSH URLs, the Git project’s Johannes Schindelin said.
“This is a Windows-only issue, as the vulnerable code is only compiled on Windows. The exploit we found involves a submodule having a name that ends in a backslash, and a maliciously-crafted SSH URL that exploits the bug to pass arbitrary options to `ssh.exe`, allowing remote code to be executed during a recursive clone.”
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The flaws were discovered and reported by Joern Schneeweisz of GitLab and by the Microsoft Security Response Center. (Microsoft bought GitHub in June 2018 for $7.5 billion and is no doubt keeping a closer eye on Git security).
“If you clone untrusted repositories, there is no workaround that avoids the risk of any vulnerabilities disclosed in this post, except for updating”, GitHub noted.
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For admins, the full list of vulnerabilities patched is as follows:
* CVE-2019-1348: The --export-marks option of git fast-import is exposed also via the in-stream command feature export-marks=... and it allows overwriting arbitrary paths. * CVE-2019-1349: When submodules are cloned recursively, under certain circumstances Git could be fooled into using the same Git directory twice. We now require the directory to be empty. * CVE-2019-1350: Incorrect quoting of command-line arguments allowed remote code execution during a recursive clone in conjunction with SSH URLs. * CVE-2019-1351: While the only permitted drive letters for physical drives on Windows are letters of the US-English alphabet, this restriction does not apply to virtual drives assigned via subst <letter>: <path>. Git mistook such paths for relative paths, allowing writing outside of the worktree while cloning. * CVE-2019-1352: Git was unaware of NTFS Alternate Data Streams, allowing files inside the .git/ directory to be overwritten during a clone. * CVE-2019-1353: When running Git in the Windows Subsystem for Linux (also known as "WSL") while accessing a working directory on a regular Windows drive, none of the NTFS protections were active. * CVE-2019-1354: Filenames on Linux/Unix can contain backslashes. On Windows, backslashes are directory separators. Git did not use to refuse to write out tracked files with such filenames. * CVE-2019-1387: Recursive clones are currently affected by a vulnerability that is caused by too-lax validation of submodule names, allowing very targeted attacks via remote code execution in recursive clones.
