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USN-4992-1: GRUB 2 vulnerabilities

18 June 2021

Several security issues were fixed in GRUB 2.

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Details

Máté Kukri discovered that the acpi command in GRUB 2 allowed privileged
users to load crafted ACPI tables when secure boot is enabled. An attacker
could use this to bypass UEFI Secure Boot restrictions. (CVE-2020-14372)

Chris Coulson discovered that the rmmod command in GRUB 2 contained a use-
after-free vulnerability. A local attacker could use this to execute
arbitrary code and bypass UEFI Secure Boot restrictions. (CVE-2020-25632)

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. (CVE-2020-27749)

It was discovered that the cutmem command in GRUB 2 did not honor secure
boot locking. A local attacker could use this to execute arbitrary code and
bypass UEFI Secure Boot restrictions. (CVE-2020-27779)

It was discovered that the option parser in GRUB 2 contained a heap
overflow vulnerability. A local attacker could use this to execute
arbitrary code and bypass UEFI Secure Boot restrictions. (CVE-2021-20225)

It was discovered that the menu rendering implementation in GRUB 2 did not
properly calculate the amount of memory needed in some situations, leading
to out-of-bounds writes. A local attacker could use this to execute
arbitrary code and bypass UEFI Secure Boot restrictions. (CVE-2021-20233)

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 20.10
Ubuntu 20.04
Ubuntu 18.04

After a standard system update you need to reboot your computer to make
all the necessary changes.

References

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Further reading