git-annex was vulnerable to the same class of security hole as git's CVE-2017-1000117. In several cases, git-annex parses a repository url, and uses it to generate a ssh command, with the hostname to ssh to coming from the url. If the hostname it parses is something like "-oProxyCommand=evil", this could result in arbitrary local code execution via ssh.

I have not bothered to try to exploit the problem, and some details of URL parsing may prevent the exploit working in some cases.

Exploiting this would involve the attacker tricking the victim into adding a remote something like "ssh://-oProxyCommand=evil/blah".

One possible avenue for an attacker that avoids exposing the URL to the user is to use initremote with a ssh remote, so embedding the URL in the git-annex branch. Then the victim would enable it with enableremote.

This was fixed in version 6.20170818. Now there's a SshHost type that is not allowed to start with a dash, and every invocation of ssh is in a function that takes a SshHost.

CVE-2017-12976 has been assigned for this issue.