CVE Vulnerabilities

CVE-2020-9452

Improper Link Resolution Before File Access ('Link Following')

Published: May 25, 2021 | Modified: Jul 12, 2022
CVSS 3.x
7.8
HIGH
Source:
NVD
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CVSS 2.x
7.2 HIGH
AV:L/AC:L/Au:N/C:C/I:C/A:C
RedHat/V2
RedHat/V3
Ubuntu

An issue was discovered in Acronis True Image 2020 24.5.22510. anti_ransomware_service.exe includes functionality to quarantine files by copying a suspected ransomware file from one directory to another using SYSTEM privileges. Because unprivileged users have write permissions in the quarantine folder, it is possible to control this privileged write with a hardlink. This means that an unprivileged user can write/overwrite arbitrary files in arbitrary folders. Escalating privileges to SYSTEM is trivial with arbitrary writes. While the quarantine feature is not enabled by default, it can be forced to copy the file to the quarantine by communicating with anti_ransomware_service.exe through its REST API.

Weakness

The product attempts to access a file based on the filename, but it does not properly prevent that filename from identifying a link or shortcut that resolves to an unintended resource.

Affected Software

Name Vendor Start Version End Version
True_image_2020 Acronis 24.5.22510 (including) 24.5.22510 (including)

Potential Mitigations

  • Follow the principle of least privilege when assigning access rights to entities in a software system.
  • Denying access to a file can prevent an attacker from replacing that file with a link to a sensitive file. Ensure good compartmentalization in the system to provide protected areas that can be trusted.

References