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  • [FreeBSD-Announce] FreeBSD Errata Notice FreeBSD-EN-18:11.listen

    From FreeBSD Errata Notices@21:1/5 to All on Thu Sep 27 21:00:01 2018
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    ============================================================================= FreeBSD-EN-18:11.listen Errata Notice
    The FreeBSD Project

    Topic: Denial of service in listen syscall over IPv6 socket

    Category: core
    Module: kernel
    Announced: 2018-09-27
    Credits: Jakub Jirasek, Secunia Research at Flexera
    Affects: All supported versions of FreeBSD.
    Corrected: 2018-09-27 18:50:10 UTC (stable/11, 11.2-STABLE)
    2018-09-27 18:34:42 UTC (releng/11.2, 11.2-RELEASE-p4)
    2018-09-27 18:34:42 UTC (releng/11.1, 11.1-RELEASE-p15)
    2018-09-27 18:48:50 UTC (stable/10, 10.4-STABLE)
    2018-09-27 18:34:42 UTC (releng/10.4, 10.4-RELEASE-p13)
    CVE Name: CVE-2018-6925

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

    I. Background

    The protocol control block is a structure that maintains the network layer state for various sockets. There are various state flags that must be
    properly maintained to keep the structure consistent.

    II. Problem Description

    There are various cases in the IPv6 socket code where the protocol control block's state flags are modified during a syscall, but are not restored if
    the operation fails. This can leave the control block in an inconsistent state.

    III. Impact

    A local unprivileged user could exploit the inconsistent state of the
    protocol control block to cause the kernel to crash, leading to a denial of service.

    IV. Workaround

    No workaround is available.

    V. Solution

    Perform one of the following:

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

    Afterward, reboot the system.

    2) To update your 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

    Afterward, reboot the system.

    3) To update your 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.

    [FreeBSD 11.x]
    # fetch https://security.FreeBSD.org/patches/EN-18:11/listen-11.patch
    # fetch https://security.FreeBSD.org/patches/EN-18:11/listen-11.patch.asc
    # gpg --verify listen-11.patch.asc

    [FreeBSD 10.4]
    # fetch https://security.FreeBSD.org/patches/EN-18:11/listen-10.patch
    # fetch https://security.FreeBSD.org/patches/EN-18:11/listen-10.patch.asc
    # gpg --verify listen-10.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/10/ r338985 releng/10.4/ r338980 stable/11/ r338986 releng/11.1/ r338980 releng/11.2/ r338980
    - -------------------------------------------------------------------------

    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://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-6925>

    For information about Secunia Research: <URL:https://www.flexerasoftware.com/enterprise/company/about/secunia-research/>

    The latest revision of this advisory is available at <URL:https://security.FreeBSD.org/advisories/FreeBSD-EN-18:11.listen.asc> -----BEGIN PGP SIGNATURE-----

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