gix-path is a crate of the gitoxide project (an implementation of git written in Rust) dealing paths and their conversions. Prior to version 0.10.11, gix-path runs git to find the path of a configuration file associated with the git installation, but improperly resolves paths containing unusual or non-ASCII characters, in rare cases enabling a local attacker to inject configuration leading to code execution. Version 0.10.11 contains a patch for the issue.
In gix_path::env, the underlying implementation of the installation_config and installation_config_prefix functions calls git config -l --show-origin to find the path of a file to treat as belonging to the git installation. Affected versions of gix-path do not pass -z/--null to cause git to report literal paths. Instead, to cover the occasional case that git outputs a quoted path, they attempt to parse the path by stripping the quotation marks. The problem is that, when a path is quoted, it may change in substantial ways beyond the concatenation of quotation marks. If not reversed, these changes can result in another valid path that is not equivalent to the original.
On a single-user system, it is not possible to exploit this, unless GIT_CONFIG_SYSTEM and GIT_CONFIG_GLOBAL have been set to unusual values or Git has been installed in an unusual way. Such a scenario is not expected. Exploitation is unlikely even on a multi-user system, though it is plausible in some uncommon configurations or use cases. In general, exploitation is more likely to succeed if users are expected to install git themselves, and are likely to do so in predictable locations; locations where git is installed, whether due to usernames in their paths or otherwise, contain characters that git quotes by default in paths, such as non-English letters and accented letters; a custom system-scope configuration file is specified with the GIT_CONFIG_SYSTEM environment variable, and its path is in an unusual location or has strangely named components; or a system-scope configuration file is absent, empty, or suppressed by means other than GIT_CONFIG_NOSYSTEM. Currently, gix-path can treat a global-scope configuration file as belonging to the installation if no higher scope configuration file is available. This increases the likelihood of exploitation even on a system where git is installed system-wide in an ordinary way. However, exploitation is expected to be very difficult even under any combination of those factors.