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  • [FreeBSD-Announce] FreeBSD Security Advisory FreeBSD-SA-19:13.pts

    From FreeBSD Security Advisories@21:1/5 to All on Tue Aug 13 05:48:35 2019
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    ============================================================================= FreeBSD-SA-19:13.pts Security Advisory
    The FreeBSD Project

    Topic: pts(4) write-after-free

    Category: core
    Module: kernel
    Announced: 2019-07-24
    Credits: syzkaller
    Affects: All supported versions of FreeBSD.
    Corrected: 2019-07-07 14:19:46 UTC (stable/12, 12.0-STABLE)
    2019-07-24 12:53:06 UTC (releng/12.0, 12.0-RELEASE-p8)
    2019-07-07 14:20:14 UTC (stable/11, 11.2-STABLE)
    2019-07-24 12:53:06 UTC (releng/11.2, 11.2-RELEASE-p12)
    2019-07-24 12:53:06 UTC (releng/11.3, 11.3-RELEASE-p1)
    CVE Name: CVE-2019-5606

    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 posix_openpt(2) system call allocates a pseudo-terminal device and
    returns a descriptor referencing that device. Such a descriptor may be configured such that a SIGIO signal will be sent to a designated process
    or process group when the device is ready to perform I/O.

    II. Problem Description

    The code which handles a close(2) of a descriptor created by
    posix_openpt(2) fails to undo the configuration which causes SIGIO to be raised. This bug can lead to a write-after-free of kernel memory.

    III. Impact

    The bug permits malicious code to trigger a write-after-free, which may
    be used to gain root privileges or escape a jail.

    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.

    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 "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-19:13/pts.patch
    # fetch https://security.FreeBSD.org/patches/SA-19:13/pts.patch.asc
    # gpg --verify pts.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/ r349805 releng/12.0/ r350282 stable/11/ r349806 releng/11.2/ r350282 releng/11.3/ r350282
    - -------------------------------------------------------------------------

    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-2019-5606>

    The latest revision of this advisory is available at <URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-19:13.pts.asc> -----BEGIN PGP SIGNATURE-----

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