#VU32926 Race condition in grub - CVE-2020-15706

Vulnerability identifier: #VU32926

Vulnerability risk: Low

CVSSv4.0: 4 [CVSS:4.0/AV:P/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Clear]

CVE-ID: CVE-2020-15706

CWE-ID: CWE-362

Exploitation vector: Local

Exploit availability: No

Vulnerable software:
grub
Universal components / Libraries / Libraries used by multiple products

Vendor: GNU

Description

The vulnerability allows a local attacker to execute arbitrary code and bypass secure boot restriction.

The vulnerability exists due to a race condition in the "grub_script_function_create()" function. An attacker with physical access can exploit the race and execute arbitrary code on the target system.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

grub: 1.99 - 2.04

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External links
https://ubuntu.com/security/notices/USN-4432-1
https://www.openwall.com/lists/oss-security/2020/07/29/3
https://access.redhat.com/security/vulnerabilities/grub2bootloader
https://lists.gnu.org/archive/html/grub-devel/2020-07/msg00034.html
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/ADV200011
https://wiki.ubuntu.com/SecurityTeam/KnowledgeBase/GRUB2SecureBootBypass
https://www.debian.org/security/2020/dsa-4735
https://www.debian.org/security/2020-GRUB-UEFI-SecureBoot
https://www.eclypsium.com/2020/07/29/theres-a-hole-in-the-boot/
https://www.openwall.com/lists/oss-security/2020/07/29/3
https://www.suse.com/c/suse-addresses-grub2-secure-boot-issue/
https://www.suse.com/support/kb/doc/?id=000019673

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Q & A

Can this vulnerability be exploited remotely?

No. The attacker should have physical access to the system in order to successfully exploit this vulnerability.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.