A vulnerability have been found in libgit2, a cross-platform, linkable library implementation of Git.
Previous versions of libgit’s SSH backend did by default not perform certificate checking if the caller did not explicitly provide a certificate check callback and so may be subjected to a man-in-the-middle attack.
For Debian 9 stretch, these problems have been fixed in version 0.25.1+really0.24.6-1+deb9u2.
We recommend that you upgrade your libgit2 packages.
Further information about Extended LTS security advisories can be found in the dedicated section of our website.