Debian DSA-3984-1: Git Shell Injection Risk in Git-CVSServer

joernchen discovered that the git-cvsserver subcommand of Git, a
distributed version control system, suffers from a shell command
injection vulnerability due to unsafe use of the Perl backtick
operator. The git-cvsserver subcommand is reachable from the
git-shell subcommand even if CVS support has not been configured
(however, the git-cvs package needs to be installed).

In addition to fixing the actual bug, this update removes the
cvsserver subcommand from git-shell by default. Refer to the updated
documentation for instructions how to reenable in case this CVS
functionality is still needed.

For the oldstable distribution (jessie), this problem has been fixed
in version 1:2.1.4-2.1+deb8u5.

For the stable distribution (stretch), this problem has been fixed in
version 1:2.11.0-3+deb9u2.

For the unstable distribution (sid), this problem has been fixed in
version 1:2.14.2-1.

We recommend that you upgrade your git packages.

Further information about Debian Security Advisories, how to apply
these updates...