Ubuntu 20.04 LTS: USN-4432-1 Critical: GRUB 2 Buffer Overflow Threat

ubuntu

July 29, 2020

Several security issues were fixed in GRUB 2.

Summary

Several security issues were fixed in GRUB 2.

Software Description:

- grub2: GRand Unified Bootloader

- grub2-signed: GRand Unified Bootloader

Details:

Jesse Michael and Mickey Shkatov discovered that the configuration parser

in GRUB2 did not properly exit when errors were discovered, resulting in

heap-based buffer overflows. A local attacker could use this to execute

arbitrary code and bypass UEFI Secure Boot restrictions. (CVE-2020-10713)

Chris Coulson discovered that the GRUB2 function handling code did not

properly handle a function being redefined, leading to a use-after-free

vulnerability. A local attacker could use this to execute arbitrary code

and bypass UEFI Secure Boot restrictions. (CVE-2020-15706)

Chris Coulson discovered that multiple integer overflows existed in GRUB2

when handling certain filesystems or font files, leading to heap-based

buffer overflows. A local attacker could use these to execute arbitrary

code and bypass UEFI Secure Boot...

Read the Full Advisory

Topics Covered

security advisory buffer overflow Ubuntu local attack GRUB 2 signed vulnerabilities

Update Instructions

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

Ubuntu 20.04 LTS:
  grub-efi-amd64-bin              2.04-1ubuntu26.1
  grub-efi-amd64-signed           1.142.3+2.04-1ubuntu26.1
  grub-efi-arm-bin                2.04-1ubuntu26.1
  grub-efi-arm64-bin              2.04-1ubuntu26.1
  grub-efi-arm64-signed           1.142.3+2.04-1ubuntu26.1
  grub-efi-ia32-bin               2.04-1ubuntu26.1

Ubuntu 18.04 LTS:
  grub-efi-amd64-bin              2.02-2ubuntu8.16
  grub-efi-amd64-signed           1.93.18+2.02-2ubuntu8.16
  grub-efi-arm-bin                2.02-2ubuntu8.16
  grub-efi-arm64-bin              2.02-2ubuntu8.16
  grub-efi-arm64-signed           1.93.18+2.02-2ubuntu8.16
  grub-efi-ia32-bin               2.02-2ubuntu8.16
  grub-efi-ia64-bin               2.02-2ubuntu8.16

Ubuntu 16.04 LTS:
  grub-efi-amd64-bin              2.02~beta2-36ubuntu3.26
  grub-efi-amd64-signed           1.66.26+2.02~beta2-36ubuntu3.26
  grub-efi-arm-bin                2.02~beta2-36ubuntu3.26
  grub-efi-arm64-bin              2.02~beta2-36ubuntu3.26
  grub-efi-arm64-signed           1.66.26+2.02~beta2-36ubuntu3.26
  grub-efi-ia32-bin               2.02~beta2-36ubuntu3.26
  grub-efi-ia64-bin               2.02~beta2-36ubuntu3.26

Ubuntu 14.04 ESM:
  grub-efi-amd64-bin              2.02~beta2-9ubuntu1.20
  grub-efi-amd64-signed           1.34.22+2.02~beta2-9ubuntu1.20
  grub-efi-arm-bin                2.02~beta2-9ubuntu1.20
  grub-efi-arm64-bin              2.02~beta2-9ubuntu1.20
  grub-efi-ia32-bin               2.02~beta2-9ubuntu1.20
  grub-efi-ia64-bin               2.02~beta2-9ubuntu1.20

Fully mitigating these vulnerabilities requires both an updated
GRUB2 boot loader and the application of a UEFI Revocation
List (dbx) to system firmware. Ubuntu will provide a packaged
dbx update at a later time, though system adminstrators may
choose to apply a third party dbx update before then. For more
details on mitigation steps and the risks entailed (especially for
dual/multi-boot scenarios), please see the Knowledge Base article at
https://wiki.ubuntu.com/SecurityTeam/KnowledgeBase/GRUB2SecureBootBypass