CVE-2020-26312: 
vulnerability analysis and mitigation

Dotmesh is a git-like command-line interface for capturing, organizing and sharing application states. In versions 0.8.1 and prior, the unsafe handling of symbolic links in an unpacking routine may enable attackers to read and/or write to arbitrary locations outside the designated target folder (GitHub Advisory).

The vulnerability exists in the untarFile routine which attempts to guard against creating symbolic links that point outside the directory a tar archive is extracted to. However, a malicious tarball can bypass this protection by first linking subdir/parent to .. (allowed, because subdir/.. falls within the archive root) and then linking subdir/parent/escapes to .., resulting in a symbolic link pointing to the tarball's parent directory, contrary to the routine's goals (GitHub Advisory).

This vulnerability may lead to arbitrary file write (with same permissions as the program running the unpack operation) if the attacker can control the archive file. Additionally, if the attacker has read access to the unpacked files, they may be able to read arbitrary system files the parent process has permissions to read (GitHub Advisory).

The vulnerability can be exploited by providing a specially crafted tar archive that contains malicious symbolic links. The attacker needs to be able to control the contents of the tar archive being processed by the application (GitHub Advisory).

As of the time of publication, no patch for this issue was available (GitHub Advisory).