About vulnerability

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.

Affected product:

AlmaLinux 9.2 ESU , Amazon Linux 2 ELS , CentOS 7 ELS , CentOS 8.4 ELS , CentOS 8.5 ELS , CentOS Stream 8 ELS , CloudLinux 7 ELS , Debian 10 ELS , Debian 11 ELS , Oracle Linux 7 ELS , RHEL 7 ELS , TuxCare 9.6 ESU , TuxCare 9.8 ESU , Ubuntu 16.04 ELS , Ubuntu 18.04 ELS , Ubuntu 20.04 ELS

Affected packages:

linux @ 5.4.0 (+17 more)

Live-patch status from KernelCare for each operating system.