Ubuntu 16.04 LTS / 18.04 LTS / 20.04 : GRUB2 regression (USN-4432-2)

Medium Nessus Plugin ID 139365

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VPR Score: 6.9

Synopsis

The remote Ubuntu host is missing one or more security-related patches.

Description

USN-4432-1 fixed vulnerabilities in GRUB2 affecting Secure Boot environments. Unfortunately, the update introduced regressions for some BIOS systems (either pre-UEFI or UEFI configured in Legacy mode), preventing them from successfully booting. This update addresses the issue. Users with BIOS systems that installed GRUB2 versions from USN-4432-1 should verify that their GRUB2 installation has a correct understanding of their boot device location and installed the boot loader correctly. We apologize for the inconvenience.

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 restrictions. (CVE-2020-14309, CVE-2020-14310, CVE-2020-14311) It was discovered that the memory allocator for GRUB2 did not validate allocation size, resulting in multiple integer overflows and heap-based buffer overflows when handling certain filesystems, PNG images or disk metadata. A local attacker could use this to execute arbitrary code and bypass UEFI Secure Boot restrictions. (CVE-2020-14308) Mathieu Trudel-Lapierre discovered that in certain situations, GRUB2 failed to validate kernel signatures. A local attacker could use this to bypass Secure Boot restrictions.
(CVE-2020-15705) Colin Watson and Chris Coulson discovered that an integer overflow existed in GRUB2 when handling the initrd command, leading to a heap-based buffer overflow. A local attacker could use this to execute arbitrary code and bypass UEFI Secure Boot restrictions. (CVE-2020-15707).

Note that Tenable Network Security has extracted the preceding description block directly from the Ubuntu security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.

Solution

Update the affected packages.

See Also

https://usn.ubuntu.com/4432-2/

Plugin Details

Severity: Medium

ID: 139365

File Name: ubuntu_USN-4432-2.nasl

Version: 1.5

Type: local

Agent: unix

Published: 2020/08/06

Updated: 2020/09/24

Dependencies: 12634

Risk Information

Risk Factor: Medium

VPR Score: 6.9

CVSS Score Source: CVE-2020-14309

CVSS v2.0

Base Score: 4.6

Temporal Score: 3.4

Vector: CVSS2#AV:L/AC:L/Au:N/C:P/I:P/A:P

Temporal Vector: CVSS2#E:U/RL:OF/RC:C

CVSS v3.0

Base Score: 6.7

Temporal Score: 5.8

Vector: CVSS:3.0/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H

Temporal Vector: CVSS:3.0/E:U/RL:O/RC:C

Vulnerability Information

CPE: p-cpe:/a:canonical:ubuntu_linux:grub-efi-amd64-bin, p-cpe:/a:canonical:ubuntu_linux:grub-efi-amd64-signed, p-cpe:/a:canonical:ubuntu_linux:grub-efi-arm-bin, p-cpe:/a:canonical:ubuntu_linux:grub-efi-arm64-bin, p-cpe:/a:canonical:ubuntu_linux:grub-efi-arm64-signed, p-cpe:/a:canonical:ubuntu_linux:grub-efi-ia32-bin, cpe:/o:canonical:ubuntu_linux:14.04, cpe:/o:canonical:ubuntu_linux:16.04, cpe:/o:canonical:ubuntu_linux:18.04:-:lts, cpe:/o:canonical:ubuntu_linux:20.04

Required KB Items: Host/cpu, Host/Ubuntu, Host/Ubuntu/release, Host/Debian/dpkg-l

Exploit Ease: No known exploits are available

Patch Publication Date: 2020/08/04

Vulnerability Publication Date: 2020/07/29

Reference Information

CVE: CVE-2020-10713, CVE-2020-14308, CVE-2020-14309, CVE-2020-14310, CVE-2020-14311, CVE-2020-15705, CVE-2020-15706, CVE-2020-15707

USN: 4432-2

IAVA: 2020-A-0349