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+=============================================================================
+FreeBSD-EN-23:21.tty                                            Errata Notice
+                                                          The FreeBSD Project
+
+Topic: tty(4) IUTF8 causes a kernel panic
+
+Category:       core
+Module:         tty
+Announced:      2023-11-24
+Affects:        FreeBSD 14.0-RELEASE
+Corrected:      2023-11-20 16:54:54 UTC (stable/14, 14.0-STABLE)
+                2023-XX-XX XX:XX:XX UTC (releng/14.0, 14.0-RELEASE-pXX)
+                2023-11-20 16:57:49 UTC (stable/13, 13.2-STABLE)
+
+For general information regarding FreeBSD Errata Notices and Security
+Advisories, including descriptions of the fields above, security
+branches, and the following sections, please visit
+<URL:https://security.FreeBSD.org/>.
+
+I.   Background
+
+The IUTF8 flag was added to the tty(4) driver in order to add proper
+backspace handling for UTF-8 characters.  Without this flag, tty(4)
+treats all characters as single-byte-wide characters and so, in the case
+of a UTF-8 character larger than two bytes, tty(4) deletes only one byte
+during a backspace event, instead of all bytes, which results in the tty
+buffer containing garbage.
+
+II.  Problem Description
+
+The implementation of backspace handling failed to check whether the TTY
+buffer was empty, in which case the kernel could panic.
+
+III. Impact
+
+An unprivileged user may be able to trigger a kernel panic.
+
+IV.  Workaround
+
+No workaround is available.
+
+V.   Solution
+
+Upgrade your 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 system via a binary patch:
+
+Systems running a RELEASE version of FreeBSD on the amd64 or arm64 platforms,
+or the i386 platfrom on FreeBSD 13 and earlier, 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 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/EN-23:XX/iutf8.patch
+# fetch https://security.FreeBSD.org/patches/EN-23:XX/iutf8.patch.asc
+# gpg --verify iutf8.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
+
+This issue is corrected as of the corresponding Git commit hash or Subversion
+revision number in the following stable and release branches:
+
+Branch/path                             Hash                     Revision
+-------------------------------------------------------------------------
+stable/14/                              ae8387cc818a	stable/14-n265760
+releng/14.0/                            XXXXXXXXXXXX  releng/14.0-nXXXXXX
+stable/13/                              8647fe60b8c3	stable/13-n256709
+-------------------------------------------------------------------------
+
+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:
+
+<URL:https://cgit.freebsd.org/src/commit/?id=NNNNNN>
+
+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
+
+VII. References
+
+<URL:https://reviews.freebsd.org/D42564>
+<URL:https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=275009>
+
+The latest revision of this advisory is available at
+<URL:https://security.FreeBSD.org/advisories/FreeBSD-EN-23:XX.iutf8.asc>