This is a security release fixing insufficient validation of submodule names (CVE-2018-11235, reported by Etienne Stalmans) and disallows .gitmodules files as symlinks. This includes libgit2 v0.27.1, whose release notes follow.

While submodule names come from the untrusted .gitmodules file, we blindly append the name to $GIT_DIR/modules to construct the final path of the submodule repository. In case the name contains e.g. ../, an adversary would be able to escape your repository and write data at arbitrary paths. In accordance with git, we now enforce some rules for submodule names which will cause libgit2 to ignore these malicious names.

Adding a symlink as .gitmodules into the index from the workdir or checking out such files is not allowed as this can make a Git implementation write outside of the repository and bypass the fsck checks for CVE-2018-11235.

libgit2 (and LibGit2Sharp) are not susceptible to CVE-2018-11233.