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  • [FreeBSD-Announce] FreeBSD Security Advisory FreeBSD-SA-20:24.ipv6

    From FreeBSD Security Advisories@21:1/5 to All on Wed Sep 2 18:00:01 2020
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    ============================================================================= FreeBSD-SA-20:24.ipv6 Security Advisory
    The FreeBSD Project

    Topic: IPv6 Hop-by-Hop options use-after-free bug

    Category: core
    Module: kernel
    Announced: 2020-09-02
    Affects: FreeBSD 11.3
    Corrected: 2020-05-07 01:28:59 UTC (stable/11, 11.4-PRERELEASE)
    2020-09-02 16:23:15 UTC (releng/11.3, 11.3-RELEASE-p13)
    CVE Name: CVE-2020-7462

    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

    IPv6 is a network layer supporting Hop-by-Hop options, which can be sent by applications via the socket API. The memory management for packet handling
    is done using mbufs.

    II. Problem Description

    Due to improper mbuf handling in the kernel, a use-after-free bug might be triggered by sending IPv6 Hop-by-Hop options over the loopback interface.

    III. Impact

    Triggering the use-after-free situation may result in unintended kernel behaviour including a kernel panic.

    IV. Workaround

    No workaround is available.

    V. Solution

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

    Perform one of the following:

    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 a 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-20:24/ipv6.patch
    # fetch https://security.FreeBSD.org/patches/SA-20:24/ipv6.patch.asc
    # gpg --verify ipv6.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/11/ r360733 releng/11.3/ r365255
    - -------------------------------------------------------------------------

    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-2020-7462>

    The latest revision of this advisory is available at <URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-20:24.ipv6.asc> -----BEGIN PGP SIGNATURE-----

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