CVE-2026-93053: speakup: keyhelp: guard letter_offsets possible out-of-range indexing

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

From: Greg Kroah-Hartman <gregkh@kernel.org>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

speakup: keyhelp: guard letter_offsets possible out-of-range indexing

help_init() builds letter_offsets[] by using the first byte of each
function name as an index via `(start & 31) - 1`. If function_names are
overridden from sysfs (root) with a name starting outside [a–z], the
index underflows or exceeds the array, leading to OOB write.

Function names can be overridden with the following commands as root:

    modprobe speakup_soft
    echo "0 _bad" > /sys/accessibility/speakup/i18n/function_names
    # then press Insert+2 on /dev/tty

This fix checks the first letter in help_init(), and if it is not in the
[a–z] range the function returns an error to the caller. Eventually this
error is propagated to drivers/accessibility/speakup/main.c:2217, which
causes a bleep sound.

The Linux kernel CVE team has assigned CVE-2026-93053 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 2.6.37 with commit c6e3fd22cd538365bfeb82997d5b89562e077d42 and fixed in 5.10.270 with commit fd339b9ef0accb2c24a5285df842552ebf5eb146
	Issue introduced in 2.6.37 with commit c6e3fd22cd538365bfeb82997d5b89562e077d42 and fixed in 5.15.221 with commit 900cd6e5ef46bd15153762fb26bb03f874fccc52
	Issue introduced in 2.6.37 with commit c6e3fd22cd538365bfeb82997d5b89562e077d42 and fixed in 6.1.188 with commit 6b39969c724d39b6062efa354dc2d38442bfd021
	Issue introduced in 2.6.37 with commit c6e3fd22cd538365bfeb82997d5b89562e077d42 and fixed in 6.6.157 with commit 2e91ab73f9beb659f581e2a6a09f79ace1140905
	Issue introduced in 2.6.37 with commit c6e3fd22cd538365bfeb82997d5b89562e077d42 and fixed in 6.12.110 with commit d7deb90c4cd086cb111f0ecc9da021218fbde1b0
	Issue introduced in 2.6.37 with commit c6e3fd22cd538365bfeb82997d5b89562e077d42 and fixed in 6.18.52 with commit 5310334762c3f08f51dc2414344dd47492c07d1d
	Issue introduced in 2.6.37 with commit c6e3fd22cd538365bfeb82997d5b89562e077d42 and fixed in 7.2.6 with commit ca4489b3e54666a7cac7294e71a3cf64e5e95286
	Issue introduced in 2.6.37 with commit c6e3fd22cd538365bfeb82997d5b89562e077d42 and fixed in 7.3-rc1 with commit 6a19ad4d68c95185308cd9e5d169b10a2cf236c8

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2026-93053
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	drivers/accessibility/speakup/keyhelp.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/fd339b9ef0accb2c24a5285df842552ebf5eb146
	https://git.kernel.org/stable/c/900cd6e5ef46bd15153762fb26bb03f874fccc52
	https://git.kernel.org/stable/c/6b39969c724d39b6062efa354dc2d38442bfd021
	https://git.kernel.org/stable/c/2e91ab73f9beb659f581e2a6a09f79ace1140905
	https://git.kernel.org/stable/c/d7deb90c4cd086cb111f0ecc9da021218fbde1b0
	https://git.kernel.org/stable/c/5310334762c3f08f51dc2414344dd47492c07d1d
	https://git.kernel.org/stable/c/ca4489b3e54666a7cac7294e71a3cf64e5e95286
	https://git.kernel.org/stable/c/6a19ad4d68c95185308cd9e5d169b10a2cf236c8