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  • [FreeBSD-Announce] FreeBSD Security Advisory FreeBSD-SA-20:14.sctp

    From FreeBSD Security Advisories@21:1/5 to All on Tue May 12 20:00:02 2020
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    ============================================================================= FreeBSD-SA-20:14.sctp Security Advisory
    The FreeBSD Project

    Topic: Improper checking in SCTP-AUTH shared key update

    Category: core
    Module: kernel
    Announced: 2020-05-12
    Credits: da_cheng_shao@yeah.net
    Affects: FreeBSD 11.3
    Corrected: 2019-09-19 10:01:19 UTC (stable/12, 12.1-STABLE)
    2019-09-19 10:06:18 UTC (stable/11, 11.3-STABLE)
    2020-05-12 16:55:32 UTC (releng/11.3, 11.3-RELEASE-p9)
    CVE Name: CVE-2019-15878

    Note: The upcoming release of FreeBSD 11.4 was branched after the original commit to the stable branch and already includes the fix for this advisory. Similarly, the 12.1 branch was created shortly after the original commit to
    the stable branch and already includes the fix.

    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

    The Stream Control Transmission Protocol (SCTP) is a transport protocol supporting the socket API. An SCTP packet consists of an SCTP common header and a number of SCTP chunks.

    The SCTP extension SCTP-AUTH can be used to authenticate SCTP chunks. It
    uses shared keys which can be managed via the socket API by the application using an SCTP association.

    II. Problem Description

    The SCTP layer does improper checking when an application tries to update
    a shared key. Therefore an unprivileged local user can trigger a use-after- free situation, for example by specific sequences of updating shared keys and closing the SCTP association.

    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-20:14/sctp.patch
    # fetch https://security.FreeBSD.org/patches/SA-20:14/sctp.patch.asc
    # gpg --verify sctp.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/ r352509 stable/11/ r352509 releng/11.3/ r360975
    - -------------------------------------------------------------------------

    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-2019-15878>

    The latest revision of this advisory is available at <URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-20:14.sctp.asc> -----BEGIN PGP SIGNATURE-----

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