CVE Vulnerabilities

CVE-2021-23240

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

Published: Jan 12, 2021 | Modified: Sep 13, 2021
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
4.4 MEDIUM
AV:L/AC:M/Au:N/C:P/I:P/A:P
RedHat/V2
RedHat/V3
7.8 MODERATE
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Ubuntu

selinux_edit_copy_tfiles in sudoedit in Sudo before 1.9.5 allows a local unprivileged user to gain file ownership and escalate privileges by replacing a temporary file with a symlink to an arbitrary file target. This affects SELinux RBAC support in permissive mode. Machines without SELinux are not vulnerable.

Weakness

The software 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
Sudo Sudo_project * *
Sudo Sudo_project 1.9.0 *
Red Hat Enterprise Linux 8 RedHat sudo-0:1.8.29-7.el8 *
Sudo Ubuntu esm-infra/xenial *
Sudo Ubuntu groovy *
Sudo Ubuntu hirsute *
Sudo Ubuntu precise/esm *
Sudo Ubuntu trusty *
Sudo Ubuntu upstream *
Sudo Ubuntu xenial *

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