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  1. #1
    Senior Member tampabay420's Avatar
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    FreeBSD-SA-03:01.cvs

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    =============================================================================
    FreeBSD-SA-03:01.cvs Security Advisory
    The FreeBSD Project

    Topic: remotely exploitable vulnerability in cvs server

    Category: contrib
    Module: contrib_cvs
    Announced: 2003-02-04
    Credits: Stefan Esser <s.esser@e-matters.de>
    Affects: All FreeBSD versions prior to 4.6-RELEASE-p7, 4.7-RELEASE-p4,
    5.0-RELEASE-p1
    Corrected: 2003-01-21 22:26:46 UTC (RELENG_4)
    2003-02-04 18:05:07 UTC (RELENG_5_0)
    2003-02-04 18:07:20 UTC (RELENG_4_7)
    2003-02-04 18:08:26 UTC (RELENG_4_6)
    FreeBSD only: NO

    I. Background

    The Concurrent Versions System (CVS) is a version control system. It
    may be used to access a repository locally, or to access a `remote
    repository' using several different methods, including `ext' (rsh),
    and `pserver' (password-authenticated server). When accessing a
    remote repository, the target machine runs the CVS server to fulfill
    client requests.

    II. Problem Description

    The implementation of the CVS server contains a programming error which
    can lead to a block of memory being freed more than once (i.e. a
    double-free bug).

    Separately, the CVS server allows clients with write access to specify
    arbitrary commands to execute as part of an update (update-prog) or
    commit (checkin-prog). This is a dangerous feature that is generally
    not needed: there are other, safer methods of triggering program
    execution.

    III. Impact

    An attacker may exploit the double-free bug in order to bypass write
    access checks. Combined with the update-prog/checkin-prog feature,
    the attacker may be able to execute arbitrary commands with the
    privileges of the CVS server. The impact is most severe when running
    the CVS server in `pserver' mode to provide read-only access to the
    world (anoncvs).

    IV. Workaround

    Do not use `pserver' mode directly. Instead, use one of the safer
    methods described in the following online resources:

    <URL:http://openbsd.sunsite.ualberta.ca/p...oncvs-paper.ps>
    <URL:http://www.netsys.com/library/papers...cvs-server.txt>

    V. Solution

    1) Upgrade your vulnerable system to 4.7-STABLE; or to the RELENG_4_7
    (4.7-RELEASE-p4), RELENG_4_6 (4.6-RELEASE-p7), or RELENG_5_0
    (5.0-RELEASE-p1) security branch dated after the correction date.

    2) To patch your present system:

    The following patch has been verified to apply to FreeBSD 4.6, 4.7, and
    5.0 systems.

    a) Download the relevant patch from the location below, and verify the
    detached PGP signature using your PGP utility.

    # fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CE...3:01/cvs.patch
    # fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CE.../cvs.patch.asc

    b) Execute the following commands as root:

    # cd /usr/src
    # patch < /path/to/patch
    # cd /usr/src/gnu/usr.bin/cvs
    # make obj && make depend && make && make install

    VI. Correction details

    The following list contains the revision numbers of each file that was
    corrected in FreeBSD.

    Path Revision
    Branch
    - -------------------------------------------------------------------------
    src/contrib/cvs/src/server.c
    RELENG_5_0 1.17.2.1
    RELENG_4_7 1.13.2.2.6.1
    RELENG_4_6 1.13.2.2.4.1
    - -------------------------------------------------------------------------

    VII. References

    <URL:http://online.securityfocus.com/archive/1/72584>
    <URL:http://security.e-matters.de/advisories/012003.html>
    <URL:http://ccvs.cvshome.org/servlets/NewsItemView?newsID=51>
    <URL:http://www.kb.cert.org/vuls/id/650937>
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    FreeBSD Users Cool ;-)
    yeah, I\'m gonna need that by friday...

  2. #2
    Banned
    Join Date
    Dec 2002
    Posts
    394
    Thx tampabay420!!

    Man I just recently bought FreeBSD 4.4 at my local comp store 2 install on my new sys
    And was thinking of running cvs in 'pserver mode' thx again.

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