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Today, the Git project released new versions to address CVE-2021-21300: a security vulnerability in the delayed checkout mechanism used by Git LFS during
git clone operations affecting versions 2.15 and newer.
These updates address an issue where a specially crafted repository can execute code during a
git clone on case-insensitive filesystems which support symbolic links by abusing certain types of clean/smudge filters, like those configured by Git LFS.
The most effective way to protect against this vulnerability is to upgrade to 2.30.2. If you can’t update immediately, you can reduce your risk by doing any of the following:
- Disable support for symbolic links in Git by running
--global core.symlinks false
- Disable support for process filters. (You can see if any of these are configured on your system by running
--show-scope --get-regexp 'filter\..*\.process'
- Avoid cloning untrusted repositories.
GitHub itself is not vulnerable to this attack. We do not store checked out copies of repositories on our servers, except for GitHub Pages, which does not use any clean/smudge filters.
Credit for finding and fixing this vulnerability is shared among Matheus Tavares and Johannes Schindelin.
1. In the Windows Command Prompt, replace the single quotes in this example with double quotes.