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Ubuntu 20.04 LTS / 22.04 LTS : GRUB2 vulnerabilities (USN-6355-1)

high Nessus Plugin ID 181178

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Synopsis

The remote Ubuntu host is missing one or more security updates.

Description

The remote Ubuntu 20.04 LTS / 22.04 LTS host has packages installed that are affected by multiple vulnerabilities as referenced in the USN-6355-1 advisory.

 - There's a possible overflow in handle_image() when shim tries to load and execute crafted EFI executables;
 The handle_image() function takes into account the SizeOfRawData field from each section to be loaded. An attacker can leverage this to perform out-of-bound writes into memory. Arbitrary code execution is not discarded in such scenario. (CVE-2022-28737)

 - A crafted 16-bit grayscale PNG image may lead to a out-of-bounds write in the heap area. An attacker may take advantage of that to cause heap data corruption or eventually arbitrary code execution and circumvent secure boot protections. This issue has a high complexity to be exploited as an attacker needs to perform some triage over the heap layout to achieve signifcant results, also the values written into the memory are repeated three times in a row making difficult to produce valid payloads. This flaw affects grub2 versions prior grub-2.12. (CVE-2021-3695)

 - A heap out-of-bounds write may heppen during the handling of Huffman tables in the PNG reader. This may lead to data corruption in the heap space. Confidentiality, Integrity and Availablity impact may be considered Low as it's very complex to an attacker control the encoding and positioning of corrupted Huffman entries to achieve results such as arbitrary code execution and/or secure boot circumvention. This flaw affects grub2 versions prior grub-2.12. (CVE-2021-3696)

 - A crafted JPEG image may lead the JPEG reader to underflow its data pointer, allowing user-controlled data to be written in heap. To a successful to be performed the attacker needs to perform some triage over the heap layout and craft an image with a malicious format and payload. This vulnerability can lead to data corruption and eventual code execution or secure boot circumvention. This flaw affects grub2 versions prior grub-2.12. (CVE-2021-3697)

 - A flaw in grub2 was found where its configuration file, known as grub.cfg, is being created with the wrong permission set allowing non privileged users to read its content. This represents a low severity confidentiality issue, as those users can eventually read any encrypted passwords present in grub.cfg.
 This flaw affects grub2 2.06 and previous versions. This issue has been fixed in grub upstream but no version with the fix is currently released. (CVE-2021-3981)

 - Integer underflow in grub_net_recv_ip4_packets; A malicious crafted IP packet can lead to an integer underflow in grub_net_recv_ip4_packets() function on rsm->total_len value. Under certain circumstances the total_len value may end up wrapping around to a small integer number which will be used in memory allocation. If the attack succeeds in such way, subsequent operations can write past the end of the buffer. (CVE-2022-28733)

 - Out-of-bounds write when handling split HTTP headers; When handling split HTTP headers, GRUB2 HTTP code accidentally moves its internal data buffer point by one position. This can lead to a out-of-bound write further when parsing the HTTP request, writing a NULL byte past the buffer. It's conceivable that an attacker controlled set of packets can lead to corruption of the GRUB2's internal memory metadata.
 (CVE-2022-28734)

 - The GRUB2's shim_lock verifier allows non-kernel files to be loaded on shim-powered secure boot systems.
 Allowing such files to be loaded may lead to unverified code and modules to be loaded in GRUB2 breaking the secure boot trust-chain. (CVE-2022-28735)

 - There's a use-after-free vulnerability in grub_cmd_chainloader() function; The chainloader command is used to boot up operating systems that doesn't support multiboot and do not have direct support from GRUB2.
 When executing chainloader more than once a use-after-free vulnerability is triggered. If an attacker can control the GRUB2's memory allocation pattern sensitive data may be exposed and arbitrary code execution can be achieved. (CVE-2022-28736)

 - When rendering certain unicode sequences, grub2's font code doesn't proper validate if the informed glyph's width and height is constrained within bitmap size. As consequence an attacker can craft an input which will lead to a out-of-bounds write into grub2's heap, leading to memory corruption and availability issues. Although complex, arbitrary code execution could not be discarded. (CVE-2022-3775)

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

Solution

Update the affected packages.

See Also

https://ubuntu.com/security/notices/USN-6355-1

Plugin Details

Severity: High

ID: 181178

File Name: ubuntu_USN-6355-1.nasl

Version: 1.1

Type: local

Agent: unix

Published: 9/8/2023

Updated: 1/17/2024

Supported Sensors: Frictionless Assessment AWS, Frictionless Assessment Azure, Frictionless Assessment Agent, Nessus Agent, Agentless Assessment, Nessus

Risk Information

VPR

Risk Factor: Medium

Score: 6.7

CVSS v2

Risk Factor: Medium

Base Score: 6.9

Temporal Score: 5.1

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

CVSS Score Source: CVE-2021-3696

CVSS v3

Risk Factor: High

Base Score: 8.1

Temporal Score: 7.1

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

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

CVSS Score Source: CVE-2022-28733

Vulnerability Information

CPE: cpe:/o:canonical:ubuntu_linux:20.04:-:lts, cpe:/o:canonical:ubuntu_linux:22.04:-:lts, p-cpe:/a:canonical:ubuntu_linux:grub-efi-amd64, 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-arm64, 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:shim, p-cpe:/a:canonical:ubuntu_linux:shim-signed

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

Exploit Ease: No known exploits are available

Patch Publication Date: 9/8/2023

Vulnerability Publication Date: 7/30/2020

Reference Information

CVE: CVE-2021-3695, CVE-2021-3696, CVE-2021-3697, CVE-2021-3981, CVE-2022-28733, CVE-2022-28734, CVE-2022-28735, CVE-2022-28736, CVE-2022-28737, CVE-2022-3775

USN: 6355-1