FreeBSD Security Advisory FreeBSD-SA-22:01.vt

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============================================================================= FreeBSD-SA-22:01.vt Security Advisory The FreeBSD Project
Topic: vt console buffer overflow
Category: kernel Module: vt Announced: 2022-01-11 Credits: Oleg Bulyzhin Affects: FreeBSD 12.2 and FreeBSD 13.0 Corrected: 2021-09-22 18:41:00 UTC (stable/13, 13.0-STABLE) 2022-01-11 18:15:03 UTC (releng/13.0, 13.0-RELEASE-p6) 2021-09-25 18:15:49 UTC (stable/12, 12.2-STABLE) 2022-01-11 18:33:21 UTC (releng/12.2, 12.2-RELEASE-p12) CVE Name: CVE-2021-29632
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I. Background
FreeBSD’s system console is provided by the vt(4) virtual terminal console driver.
II. Problem Description
Under certain conditions involving use of the highlight buffer while text is scrolling on the console, console data may overwrite data structures associated with the system console or other kernel memory.
III. Impact
Users with access to the system console may be able to cause system misbehaviour.
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 security.FreeBSD.org/patches/SA-22:01/vt.patch # fetch security.FreeBSD.org/patches/SA-22:01/vt.patch.asc # gpg –verify vt.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 and 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/ 9352de39c3dc stable/13-n247428 releng/13.0/ 3e0a1e124169 releng/13.0-n244773 stable/12/ r370674 releng/12.2/ r371491 – ————————————————————————-
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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