• [FreeBSD-Announce] FreeBSD Security Advisory FreeBSD-SA-19:22.mbuf

    From FreeBSD Security Advisories@21:1/5 to All on Tue Aug 20 21:00:01 2019
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    ============================================================================= FreeBSD-SA-19:22.mbuf Security Advisory
    The FreeBSD Project

    Topic: IPv6 remote Denial-of-Service

    Category: kernel
    Module: net
    Announced: 2019-08-20
    Credits: Clement Lecigne
    Affects: All supported versions of FreeBSD.
    Corrected: 2019-08-10 00:01:25 UTC (stable/12, 12.0-STABLE)
    2019-08-20 17:49:33 UTC (releng/12.0, 12.0-RELEASE-p10)
    2019-08-10 00:02:45 UTC (stable/11, 11.3-STABLE)
    2019-08-20 17:49:33 UTC (releng/11.3, 11.3-RELEASE-p3)
    2019-08-20 17:49:33 UTC (releng/11.2, 11.2-RELEASE-p14)
    CVE Name: CVE-2019-5611

    For general information regarding FreeBSD Security Advisories, including descriptions of the fields above, security branches, and the following sections, please visit <URL:https://security.FreeBSD.org/>.

    I. Background

    mbufs are a unit of memory management mostly used in the kernel for network packets and socket buffers. m_pulldown(9) is a function to arrange the data
    in a chain of mbufs.

    II. Problem Description

    Due do a missing check in the code of m_pulldown(9) data returned may not be contiguous as requested by the caller.

    III. Impact

    Extra checks in the IPv6 code catch the error condition and trigger a kernel panic leading to a remote DoS (denial-of-service) attack with certain
    Ethernet interfaces. At this point it is unknown if any other than the IPv6 code paths can trigger a similar condition.

    IV. Workaround

    For the currently known attack vector systems with IPv6 not enabled are not vulnerable.

    On systems with IPv6 active, IPv6 fragmentation may be disabled, or
    a firewall can be used to filter out packets with certain or excessive
    amounts of extension headers in a first fragment. These rules may be
    dependent on the operational needs of each site.

    V. Solution

    Upgrade your vulnerable system to a supported FreeBSD stable or
    release / security branch (releng) dated after the correction date,
    and reboot.

    1) To update your vulnerable system via a binary patch:

    Systems running a RELEASE version of FreeBSD on the i386 or amd64
    platforms can be updated via the freebsd-update(8) utility:

    # freebsd-update fetch
    # freebsd-update install
    # shutdown -r +10min "Rebooting for security update"

    2) To update your vulnerable system via a source code patch:

    The following patches have been verified to apply to the applicable
    FreeBSD release branches.

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

    # fetch https://security.FreeBSD.org/patches/SA-19:22/mbuf.patch
    # fetch https://security.FreeBSD.org/patches/SA-19:22/mbuf.patch.asc
    # gpg --verify mbuf.patch.asc

    b) Apply the patch. Execute the following commands as root:

    # cd /usr/src
    # patch < /path/to/patch

    c) Recompile your kernel as described in <URL:https://www.FreeBSD.org/handbook/kernelconfig.html> and reboot the
    system.

    VI. Correction details

    The following list contains the correction revision numbers for each
    affected branch.

    Branch/path Revision
    - ------------------------------------------------------------------------- stable/12/ r350828 releng/12.0/ r351259 stable/11/ r350829 releng/11.3/ r351259 releng/11.2/ r351259
    - -------------------------------------------------------------------------

    To see which files were modified by a particular revision, run the
    following command, replacing NNNNNN with the revision number, on a
    machine with Subversion installed:

    # svn diff -cNNNNNN --summarize svn://svn.freebsd.org/base

    Or visit the following URL, replacing NNNNNN with the revision number:

    <URL:https://svnweb.freebsd.org/base?view=revision&revision=NNNNNN>

    VII. References

    <URL:https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=238787> <URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2019-5611>

    The latest revision of this advisory is available at <URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-19:22.mbuf.asc> -----BEGIN PGP SIGNATURE-----

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