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=============================================================================
FreeBSD-SA-19:18.bzip2                                      Security Advisory
                                                          The FreeBSD Project

Topic:          Multiple vulnerabilities in bzip2

Category:       contrib
Module:         bzip2
Announced:      2019-08-06
Affects:        All supported versions of FreeBSD.
Corrected:      2019-07-04 07:29:18 UTC (stable/12, 12.0-STABLE)
                2019-08-06 17:09:47 UTC (releng/12.0, 12.0-RELEASE-p9)
                2019-07-04 07:32:25 UTC (stable/11, 11.3-STABLE)
                2019-08-06 17:09:47 UTC (releng/11.3, 11.3-RELEASE-p2)
                2019-08-06 17:09:47 UTC (releng/11.2, 11.2-RELEASE-p13)
CVE Name:       CVE-2016-3189, CVE-2019-12900

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 bzip2(1)/bunzip2(1) utilities and the libbz2 library compress and
decompress files using an algorithm based on the Burrows-Wheeler transform.
They are generally slower than Lempel-Ziv compressors such as gzip, but
usually provide a greater compression ratio.

The bzip2recover utility extracts blocks from a damaged bzip2(1) file,
permitting partial recovery of the contents of the file.

II.  Problem Description

The decompressor used in bzip2 contains a bug which can lead to an
out-of-bounds write when processing a specially crafted bzip2(1) file.

bzip2recover contains a heap use-after-free bug which can be triggered
when processing a specially crafted bzip2(1) file.

III. Impact

An attacker who can cause maliciously crafted input to be processed
may trigger either of these bugs.  The bzip2recover bug may cause a
crash, permitting a denial-of-service.  The bzip2 decompressor bug
could potentially be exploited to execute arbitrary code.

Note that some utilities, including the tar(1) archiver and the bspatch(1)
binary patching utility (used in portsnap(8) and freebsd-update(8))
decompress bzip2(1)-compressed data internally; system administrators should
assume that their systems will at some point decompress bzip2(1)-compressed
data even if they never explicitly invoke the bunzip2(1) utility.

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 restart daemons if necessary.

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

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-19:18/bzip2.patch
# fetch https://security.FreeBSD.org/patches/SA-19:18/bzip2.patch.asc
# gpg --verify bzip2.patch.asc

b) Apply the patch.  Execute the following commands as root:

# cd /usr/src
# patch < /path/to/patch

c) Recompile the operating system using buildworld and installworld as
described in <URL:https://www.FreeBSD.org/handbook/makeworld.html>.

Restart all daemons that use the library, or reboot the system.

VI.  Correction details

The following list contains the correction revision numbers for each
affected branch.

Branch/path                                                      Revision
- -------------------------------------------------------------------------
stable/12/                                                        r349717
releng/12.0/                                                      r350643
stable/11/                                                        r349718
releng/11.3/                                                      r350643
releng/11.2/                                                      r350643
- -------------------------------------------------------------------------

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-2016-3189>
<URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2019-12900>

The latest revision of this advisory is available at
<URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-19:18.bzip2.asc>
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