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FreeBSD Security Advisory FreeBSD-SA-22:08.zlib

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FreeBSD-SA-22:08.zlib                                       Security Advisory
                                                          The FreeBSD Project

Topic:          zlib compression out-of-bounds write

Category:       zlib
Module:         contrib
Announced:      2022-04-06
Credits:        Danilo Ramos of Eideticom
                Tavis Ormandy of Google Project Zero
Affects:        All supported versions of FreeBSD.
Corrected:      2022-04-04 19:30:33 UTC (stable/13, 13.1-STABLE)
                2022-04-04 20:02:42 UTC (releng/13.1, 13.1-RC1-p1)
                2022-04-06 03:04:19 UTC (releng/13.0, 13.0-RELEASE-p11)
                2022-04-04 01:07:59 UTC (stable/12, 12.3-STABLE)
                2022-04-06 03:06:39 UTC (releng/12.3, 12.3-RELEASE-p5)
CVE Name:       CVE-2018-25032

For general information regarding FreeBSD Security Advisories,
including descriptions of the fields above, security branches, and the
following sections, please visit <URL:>.

I.   Background

zlib is a compression library used by numerous applications, as well as some
FreeBSD kernel components, to provide data compression/decompression

II.  Problem Description

Certain inputs can cause zlib's compression routine to overwrite an internal
buffer with compressed data.  This issue may require the use of uncommon or
non-default compression parameters.

III. Impact

The out-of-bounds write may result in memory corruption and an application
crash or 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 amd64, i386, or
(on FreeBSD 13 and later) arm64 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
# fetch
# gpg --verify zlib.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

Recompile the operating system using buildworld and installworld as
described in <URL:>.

Reboot the system.

VI.  Correction details

This issue is corrected by the corresponding Git commit hash or Subversion
revision number in the following stable and release branches:

Branch/path                             Hash                     Revision
- -------------------------------------------------------------------------
stable/13/                              c4727a47f18c    stable/13-n250251
releng/13.1/                            f5196112e8bd  releng/13.1-n250070
releng/13.0/                            9854ff088002  releng/13.0-n244799
stable/12/                                                        r371856
releng/12.3/                                                      r371875
- -------------------------------------------------------------------------

For FreeBSD 13 and later:

Run the following command to see which files were modified by a
particular commit:

# git show --stat <commit hash>

Or visit the following URL, replacing NNNNNN with the hash:


To determine the commit count in a working tree (for comparison against
nNNNNNN in the table above), run:

# git rev-list --count --first-parent HEAD

For FreeBSD 12 and earlier:

Run the following command to see which files were modified by a particular
revision, replacing NNNNNN with the revision number:

# svn diff -cNNNNNN --summarize svn://

Or visit the following URL, replacing NNNNNN with the revision number:


VII. References

<other info on vulnerability>


The latest revision of this advisory is available at