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FreeBSD-SA-19:19.mldv2                                      Security Advisory
                                                          The FreeBSD Project

Topic:          ICMPv6 / MLDv2 out-of-bounds memory access

Category:       core
Module:         net
Announced:      2019-08-06
Credits:        CJD of Apple
Affects:        All supported versions of FreeBSD.
Corrected:      2019-08-06 17:13:41 UTC (stable/12, 12.0-STABLE)
                2019-08-06 17:11:17 UTC (releng/12.0, 12.0-RELEASE-p9)
                2019-08-06 17:15:46 UTC (stable/11, 11.3-STABLE)
                2019-08-06 17:11:17 UTC (releng/11.3, 11.3-RELEASE-p2)
                2019-08-06 17:11:17 UTC (releng/11.2, 11.2-RELEASE-p13)
CVE Name:       CVE-2019-5608

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

MLDv2 is the Multicast Listener Discovery protocol, version 2.  It is used
by IPv6 routers to discover multicast listeners.

II.  Problem Description

The ICMPv6 input path incorrectly handles cases where an MLDv2 listener
query packet is internally fragmented across multiple mbufs.

III. Impact

A remote attacker may be able to cause an out-of-bounds read or write that
may cause the kernel to attempt to access an unmapped page and subsequently
panic.

IV.  Workaround

No workaround is available.  Systems not using IPv6 are not affected.

V.   Solution

Perform one of the following:

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 "Reboot 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.

[FreeBSD 11.2, FreeBSD 11.3]
# fetch https://security.FreeBSD.org/patches/SA-19:19/mldv2.11.patch
# fetch https://security.FreeBSD.org/patches/SA-19:19/mldv2.11.patch.asc
# gpg --verify mldv2.11.patch.asc

[FreeBSD 12.0]
# fetch https://security.FreeBSD.org/patches/SA-19:19/mldv2.12.patch
# fetch https://security.FreeBSD.org/patches/SA-19:19/mldv2.12.patch.asc
# gpg --verify mldv2.12.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/                                                        r350648
releng/12.0/                                                      r350644
stable/11/                                                        r350650
releng/11.3/                                                      r350644
releng/11.2/                                                      r350644
- -------------------------------------------------------------------------

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-2019-5608>

The latest revision of this advisory is available at
<URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-19:19.mldv2.asc>
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