CVE Vulnerabilities

CVE-2020-27779

Improper Authorization

Published: Mar 03, 2021 | Modified: Nov 21, 2024
CVSS 3.x
7.5
HIGH
Source:
NVD
CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:H
CVSS 2.x
6.9 MEDIUM
AV:L/AC:M/Au:N/C:C/I:C/A:C
RedHat/V2
RedHat/V3
7.5 MODERATE
CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:H
Ubuntu
MEDIUM

A flaw was found in grub2 in versions prior to 2.06. The cutmem command does not honor secure boot locking allowing an privileged attacker to remove address ranges from memory creating an opportunity to circumvent SecureBoot protections after proper triage about grubs memory layout. The highest threat from this vulnerability is to data confidentiality and integrity as well as system availability.

Weakness

The product does not perform or incorrectly performs an authorization check when an actor attempts to access a resource or perform an action.

Affected Software

Name Vendor Start Version End Version
Grub2 Gnu * 2.06 (excluding)
Red Hat Enterprise Linux 7 RedHat grub2-1:2.02-0.87.el7_9.2 *
Red Hat Enterprise Linux 7.2 Advanced Update Support RedHat grub2-1:2.02-0.86.el7_2.2 *
Red Hat Enterprise Linux 7.3 Advanced Update Support RedHat grub2-1:2.02-0.86.el7_3.2 *
Red Hat Enterprise Linux 7.4 Advanced Update Support RedHat grub2-1:2.02-0.86.el7_4.2 *
Red Hat Enterprise Linux 7.4 Telco Extended Update Support RedHat grub2-1:2.02-0.86.el7_4.2 *
Red Hat Enterprise Linux 7.4 Update Services for SAP Solutions RedHat grub2-1:2.02-0.86.el7_4.2 *
Red Hat Enterprise Linux 7.6 Extended Update Support RedHat grub2-1:2.02-0.86.el7_6.3 *
Red Hat Enterprise Linux 7.7 Extended Update Support RedHat grub2-1:2.02-0.86.el7_7.3 *
Red Hat Enterprise Linux 8 RedHat grub2-1:2.02-90.el8_3.1 *
Red Hat Enterprise Linux 8 RedHat shim-0:15.4-2.el8_1 *
Red Hat Enterprise Linux 8 RedHat shim-unsigned-aarch64-0:15-7.el8_1 *
Red Hat Enterprise Linux 8 RedHat shim-unsigned-x64-0:15.4-4.el8_1 *
Red Hat Enterprise Linux 8 RedHat fwupd-0:1.5.9-1.el8_4 *
Red Hat Enterprise Linux 8.1 Extended Update Support RedHat grub2-1:2.02-87.el8_1.2 *
Red Hat Enterprise Linux 8.1 Extended Update Support RedHat fwupd-0:1.1.4-4.el8_1 *
Red Hat Enterprise Linux 8.1 Extended Update Support RedHat shim-0:15.4-2.el8_1 *
Red Hat Enterprise Linux 8.1 Extended Update Support RedHat shim-unsigned-aarch64-0:15-7.el8_1 *
Red Hat Enterprise Linux 8.1 Extended Update Support RedHat shim-unsigned-x64-0:15.4-4.el8_1 *
Red Hat Enterprise Linux 8.2 Extended Update Support RedHat grub2-1:2.02-87.el8_2.3 *
Red Hat Enterprise Linux 8.2 Extended Update Support RedHat fwupd-0:1.1.4-9.el8_2 *
Red Hat Enterprise Linux 8.2 Extended Update Support RedHat shim-0:15.4-2.el8_1 *
Red Hat Enterprise Linux 8.2 Extended Update Support RedHat shim-unsigned-aarch64-0:15-7.el8_1 *
Red Hat Enterprise Linux 8.2 Extended Update Support RedHat shim-unsigned-x64-0:15.4-4.el8_1 *
Grub2 Ubuntu bionic *
Grub2 Ubuntu trusty *
Grub2 Ubuntu xenial *
Grub2-signed Ubuntu bionic *
Grub2-signed Ubuntu esm-infra-legacy/trusty *
Grub2-signed Ubuntu focal *
Grub2-signed Ubuntu groovy *
Grub2-signed Ubuntu hirsute *
Grub2-signed Ubuntu impish *
Grub2-signed Ubuntu trusty *
Grub2-signed Ubuntu trusty/esm *
Grub2-signed Ubuntu xenial *
Grub2-unsigned Ubuntu bionic *
Grub2-unsigned Ubuntu focal *
Grub2-unsigned Ubuntu groovy *
Grub2-unsigned Ubuntu hirsute *
Grub2-unsigned Ubuntu impish *
Grub2-unsigned Ubuntu precise/esm *
Grub2-unsigned Ubuntu trusty *
Grub2-unsigned Ubuntu xenial *

Extended Description

Assuming a user with a given identity, authorization is the process of determining whether that user can access a given resource, based on the user’s privileges and any permissions or other access-control specifications that apply to the resource. When access control checks are not applied consistently - or not at all - users are able to access data or perform actions that they should not be allowed to perform. This can lead to a wide range of problems, including information exposures, denial of service, and arbitrary code execution.

Potential Mitigations

  • Divide the product into anonymous, normal, privileged, and administrative areas. Reduce the attack surface by carefully mapping roles with data and functionality. Use role-based access control (RBAC) to enforce the roles at the appropriate boundaries.
  • Note that this approach may not protect against horizontal authorization, i.e., it will not protect a user from attacking others with the same role.
  • Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
  • For example, consider using authorization frameworks such as the JAAS Authorization Framework [REF-233] and the OWASP ESAPI Access Control feature [REF-45].
  • For web applications, make sure that the access control mechanism is enforced correctly at the server side on every page. Users should not be able to access any unauthorized functionality or information by simply requesting direct access to that page.
  • One way to do this is to ensure that all pages containing sensitive information are not cached, and that all such pages restrict access to requests that are accompanied by an active and authenticated session token associated with a user who has the required permissions to access that page.

References