This is a security release fixing the following issues:
CVE-2019-1348: the fast-import stream command "feature export-marks=path" allows writing to arbitrary file paths. As libgit2 does not offer any interface for fast-import, it is not susceptible to this vulnerability.
CVE-2019-1349: by using NTFS 8.3 short names, backslashes or alternate filesystreams, it is possible to cause submodules to be written into pre-existing directories during a recursive clone using git. As libgit2 rejects cloning into non-empty directories by default, it is not susceptible to this vulnerability.
CVE-2019-1350: recursive clones may lead to arbitrary remote code executing due to improper quoting of command line arguments. As libgit2 uses libssh2, which does not require us to perform command line parsing, it is not susceptible to this vulnerability.
CVE-2019-1351: Windows provides the ability to substitute drive letters with arbitrary letters, including multi-byte Unicode letters. To fix any potential issues arising from interpreting such paths as relative paths, we have extended detection of DOS drive prefixes to accomodate for such cases.
CVE-2019-1352: by using NTFS-style alternative file streams for the ".git" directory, it is possible to overwrite parts of the repository. While this has been fixed in the past for Windows, the same vulnerability may also exist on other systems that write to NTFS filesystems. We now reject any paths starting with ".git:" on all systems.
CVE-2019-1353: by using NTFS-style 8.3 short names, it was possible to write to the ".git" directory and thus overwrite parts of the repository, leading to possible remote code execution. While this problem was already fixed in the past for Windows, other systems accessing NTFS filesystems are vulnerable to this issue too. We now enable NTFS protecions by default on all systems to fix this attack vector.
CVE-2019-1354: on Windows, backslashes are not a valid part of a filename but are instead interpreted as directory separators. As other platforms allowed to use such paths, it was possible to write such invalid entries into a Git repository and was thus an attack vector to write into the ".git" dierctory. We now reject any entries starting with ".git" on all systems.
CVE-2019-1387: it is possible to let a submodule's git directory point into a sibling's submodule directory, which may result in overwriting parts of the Git repository and thus lead to arbitrary command execution. As libgit2 doesn't provide any way to do submodule clones natively, it is not susceptible to this vulnerability. Users of libgit2 that have implemented recursive submodule clones manually are encouraged to review their implementation for this vulnerability.