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USN-6355-1: GRUB2 vulnerabilities

8 September 2023

Several security issues were fixed in GRUB2.

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Releases

Packages

  • grub2-signed - GRand Unified Bootloader
  • grub2-unsigned - GRand Unified Bootloader
  • shim - boot loader to chain-load signed boot loaders under Secure Boot
  • shim-signed - Secure Boot chain-loading bootloader (Microsoft-signed binary)

Details

Daniel Axtens discovered that specially crafted images could cause a
heap-based out-of-bonds write. A local attacker could possibly use
this to circumvent secure boot protections. (CVE-2021-3695)

Daniel Axtens discovered that specially crafted images could cause
out-of-bonds read and write. A local attacker could possibly use this
to circumvent secure boot protections. (CVE-2021-3696)

Daniel Axtens discovered that specially crafted images could cause
buffer underwrite which allows arbitrary data to be written to a heap.
A local attacker could possibly use this to circumvent secure
boot protections. (CVE-2021-3697)

It was discovered that GRUB2 configuration files were created with
the wrong permissions. An attacker could possibly use this to leak
encrypted passwords. (CVE-2021-3981)

Daniel Axtens discovered that specially crafted IP packets could cause
an integer underflow and write past the end of a bugger. An attacker
could possibly use this to circumvent secure boot protections.
(CVE-2022-28733)

Daniel Axtens discovered that specially crafted HTTP headers can cause
an out-of-bounds write of a NULL byte. An attacker could possibly use
this to corrupt GRUB2's internal data. (CVE-2022-28734)

Julian Andres Klode discovered that GRUB2 shim_lock allowed non-
kernel files to be loaded. A local attack could possibly use this to
circumvent secure boot protections. (CVE-2022-28735)

Chris Coulson discovered that executing chainloaders more than once
caused a use-after-free vulnerability. A local attack could possibly
use this to circumvent secure boot protections. (CVE-2022-28736)

Chris Coulson discovered that specially crafted executables could
cause shim to make out-of-bound writes. A local attack could possibly
use this to circumvent secure boot protections. (CVE-2022-28737)

Zhang Boyang discovered that specially crafted unicode sequences
could lead to an out-of-bounds write to a heap. A local attacker could
possibly use this to circumvent secure boot protections.
(CVE-2022-3775)

Reduce your security exposure

Ubuntu Pro provides ten-year security coverage to 25,000+ packages in Main and Universe repositories, and it is free for up to five machines.

Learn more about Ubuntu Pro

Update instructions

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

Ubuntu 22.04
Ubuntu 20.04

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

References

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Further reading