Arbitrary code execution when checking out an attacker-controlled Git branch

Summary

Cygwin Git is a patch set for the git command line tool for the cygwin environment. A specially crafted repository that contains symbolic links as well as files with backslash characters in the file name may cause just-checked out code to be executed while checking out a repository using Git on Cygwin. The problem will be patched in the Cygwin Git v2.31.1-2 release. At time of writing, the vulnerability is present in the upstream Git source code; any Cygwin user who compiles Git for themselves from upstream sources should manually apply a patch to mitigate the vulnerability. As mitigation users should not clone or pull from repositories from untrusted sources. CVE-2019-1354 was an equivalent vulnerability in Git for Visual Studio.