A GRUB2 security update has been released for Ubuntu Linux 20.04 LTS, 22.04 LTS, and 23.04.

[USN-6410-1] GRUB2 vulnerabilities

==========================================================================
Ubuntu Security Notice USN-6410-1
October 04, 2023

grub2-signed, grub2-unsigned vulnerabilities
==========================================================================

A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 23.04
- Ubuntu 22.04 LTS
- Ubuntu 20.04 LTS

Summary:

Several security issues were fixed in GRUB2.

Software Description:
- grub2-signed: GRand Unified Bootloader
- grub2-unsigned: GRand Unified Bootloader

Details:

It was discovered that a specially crafted file system image could cause a
heap-based out-of-bounds write. A local attacker could potentially use this
to perform arbitrary code execution bypass and bypass secure boot
protections. (CVE-2023-4692)

It was discovered that a specially crafted file system image could cause an
out-of-bounds read. A physically-present attacker could possibly use this
to leak sensitive information to the GRUB pager. (CVE-2023-4693)

Update instructions:

The problem can be corrected by updating your system to the following
package versions:

Ubuntu 23.04:
grub-efi-amd64 2.06-2ubuntu17.2
grub-efi-amd64-bin 2.06-2ubuntu17.220:32
grub-efi-amd64-signed 1.193.2+2.06-2ubuntu17.2
grub-efi-arm64 2.06-2ubuntu17.2
grub-efi-arm64-bin 2.06-2ubuntu17.2
grub-efi-arm64-signed 1.193.2+2.06-2ubuntu17.2

Ubuntu 22.04 LTS:
grub-efi-amd64 2.06-2ubuntu14.4
grub-efi-amd64-bin 2.06-2ubuntu14.4
grub-efi-amd64-signed 1.187.6+2.06-2ubuntu14.4
grub-efi-arm64 2.06-2ubuntu14.4
grub-efi-arm64-bin 2.06-2ubuntu14.4
grub-efi-arm64-signed 1.187.6+2.06-2ubuntu14.4

Ubuntu 20.04 LTS:
grub-efi-amd64-signed 1.187.6~20.04.1+2.06-2ubuntu14.4
grub-efi-arm64-signed 1.187.6~20.04.1+2.06-2ubuntu14.4

In general, a standard system update will make all the necessary changes.

References:
https://ubuntu.com/security/notices/USN-6410-1
CVE-2023-4692, CVE-2023-4693

Package Information:
https://launchpad.net/ubuntu/+source/grub2-signed/1.193.2
https://launchpad.net/ubuntu/+source/grub2-unsigned/2.06-2ubuntu17.2
https://launchpad.net/ubuntu/+source/grub2-signed/1.187.6
https://launchpad.net/ubuntu/+source/grub2-unsigned/2.06-2ubuntu14.4
https://launchpad.net/ubuntu/+source/grub2-signed/1.187.6~20.04.1