FreeBSD Security Advisory FreeBSD-SA-22:05.bhyve


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============================================================================= FreeBSD-SA-22:05.bhyve Security Advisory The FreeBSD Project
Topic: Bhyve e82545 device emulation out-of-bounds write
Category: core Module: bhyve Announced: 2022-04-06 Credits: Mehdi Talbi, Synacktiv Affects: All supported versions of FreeBSD. Corrected: 2022-04-05 22:59:52 UTC (stable/13, 13.1-STABLE) 2022-04-06 01:56:57 UTC (releng/13.1, 13.1-RC1-p1) 2022-04-06 03:04:14 UTC (releng/13.0, 13.0-RELEASE-p11) 2022-04-05 23:03:35 UTC (stable/12, 12.3-STABLE) 2022-04-06 03:06:28 UTC (releng/12.3, 12.3-RELEASE-p5) CVE Name: CVE-2022-23087
For general information regarding FreeBSD Security Advisories, including descriptions of the fields above, security branches, and the following sections, please visit .
I. Background
bhyve(8) is a hypervisor that supports running a variety of guest operating systems in virtual machines. It implements a number of device models, including an emulated Intel 82545 network interface adapter.
II. Problem Description
The e1000 network adapters permit a variety of modifications to an Ethernet packet when it is being transmitted. These include the insertion of IP and TCP checksums, insertion of an Ethernet VLAN header, and TCP segmentation offload (“TSO”). The e1000 device model uses an on-stack buffer to generate the modified packet header when simulating these modifications on transmitted packets.
When checksum offload is requested for a transmitted packet, the e1000 device model used a guest-provided value to specify the checksum offset in the on- stack buffer. The offset was not validated for certain packet types.
III. Impact
A misbehaving bhyve guest could overwrite memory in the bhyve process on the host, possibly leading to code execution in the host context.
The bhyve process runs in a Capsicum sandbox, which (depending on the FreeBSD version and bhyve configuration) limits the impact of exploiting this issue.
IV. Workaround
Only the e1000 device model is affected; the virtio-net device is not affected by this issue. If supported by the guest operating system, presenting only the virtio-net device to the guest is a suitable workaround. No workaround is available if the e1000 device model is required.
V. Solution
Upgrade your vulnerable system to a supported FreeBSD stable or release / security branch (releng) dated after the correction date, and restart bhyve virtual machines.
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 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 security.FreeBSD.org/patches/SA-22:05/bhyve.patch # fetch security.FreeBSD.org/patches/SA-22:05/bhyve.patch.asc # gpg –verify bhyve.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 .
Restart the applicable bhyve virtual machines, or 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/ 53f722094798 stable/13-n250272 releng/13.1/ 5a28d8befda0 releng/13.1-n250078 releng/13.0/ b85c68857da3 releng/13.0-n244795 stable/12/ r371867 releng/12.3/ r371871 – ————————————————————————-
For FreeBSD 13 and later:
Run the following command to see which files were modified by a particular commit:
# git show –stat
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://svn.freebsd.org/base
Or visit the following URL, replacing NNNNNN with the revision number:

VII. References

The latest revision of this advisory is available at —–BEGIN PGP SIGNATURE—–
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