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CVE-2020-27749

Published: 2 March 2021

A flaw was found in grub2 in versions prior to 2.06. Variable names present are expanded in the supplied command line into their corresponding variable contents, using a 1kB stack buffer for temporary storage, without sufficient bounds checking. If the function is called with a command line that references a variable with a sufficiently large payload, it is possible to overflow the stack buffer, corrupt the stack frame and control execution which could also circumvent Secure Boot protections. The highest threat from this vulnerability is to data confidentiality and integrity as well as system availability.

From the Ubuntu security team

Chris Coulson discovered that a buffer overflow existed in the command line parser in GRUB 2. A local attacker could use this to execute arbitrary code and bypass UEFI Secure Boot restrictions.

Priority

Medium

CVSS 3 base score: 7.5

Status

Package Release Status
grub2-signed
Launchpad, Ubuntu, Debian
bionic
Released (1.167~18.04.5)
focal
Released (1.167.2)
groovy
Released (1.167.2)
hirsute
Released (1.164)
impish
Released (1.169)
jammy
Released (1.169)
precise Does not exist

trusty Needs triage

upstream Needs triage

xenial Pending
(1.164)
grub2-unsigned
Launchpad, Ubuntu, Debian
bionic
Released (2.04-1ubuntu44.1.2)
focal
Released (2.04-1ubuntu44.2)
groovy
Released (2.04-1ubuntu44.2)
hirsute
Released (2.04-1ubuntu42)
impish
Released (2.04-1ubuntu45)
jammy
Released (2.04-1ubuntu45)
precise Ignored
(end of ESM support, was needs-triage)
trusty Needs triage

upstream Needs triage

xenial Pending
(2.04-1ubuntu42)

Notes

AuthorNote
sbeattie
grub2-unsigned will contain fixes and supersede grub2, which will contain only BIOS grub bits.

References

Bugs