-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA512

=============================================================================
FreeBSD-SA-18:12.elf                                        Security Advisory
                                                          The FreeBSD Project

Topic:          Improper ELF header parsing

Category:       core
Module:         kernel
Announced:      2018-09-12
Credits:        Thomas Barabosch, Fraunhofer FKIE; Mark Johnston
Affects:        All supported versions of FreeBSD.
Corrected:      2018-09-12 05:02:11 UTC (stable/11, 11.1-STABLE)
                2018-09-12 05:07:35 UTC (releng/11.2, 11.2-RELEASE-p3)
                2018-09-12 05:07:35 UTC (releng/11.1, 11.1-RELEASE-p14)
                2018-09-12 05:03:30 UTC (stable/10, 10.4-STABLE)
                2018-09-12 05:07:35 UTC (releng/10.4, 10.4-RELEASE-p12)
CVE Name:       CVE-2018-6924

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

To execute a binary the kernel must parse the ELF header to determine the
entry point address, the program interpreter, and other parameters.

II.  Problem Description

Insufficient validation was performed in the ELF header parser, and malformed
or otherwise invalid ELF binaries were not rejected as they should be.

III. Impact

Execution of a malicious ELF binary may result in a kernel crash or may
disclose kernel memory.

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.

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 +30 "Rebooting 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.

# fetch https://security.FreeBSD.org/patches/SA-18:12/elf.patch
# fetch https://security.FreeBSD.org/patches/SA-18:12/elf.patch.asc
# gpg --verify elf.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/                                                        r338605
releng/10.4/                                                      r338606
stable/11/                                                        r338604
releng/11.1/                                                      r338606
releng/11.2/                                                      r338606
- -------------------------------------------------------------------------

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-2018-6924>

The latest revision of this advisory is available at
<URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-18:12.elf.asc>
-----BEGIN PGP SIGNATURE-----
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=J/a5
-----END PGP SIGNATURE-----