CVE Vulnerabilities

CVE-2021-32555

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

Published: Jun 12, 2021 | Modified: Jun 16, 2021
CVSS 3.x
5.5
MEDIUM
Source:
NVD
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
CVSS 2.x
2.1 LOW
AV:L/AC:L/Au:N/C:P/I:N/A:N
RedHat/V2
RedHat/V3
Ubuntu
MEDIUM

It was discovered that read_file() in apport/hookutils.py would follow symbolic links or open FIFOs. When this function is used by the xorg-hwe-18.04 package apport hooks, it could expose private data to other local users.

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
Ubuntu_linux Canonical 18.04 (including) 18.04 (including)
Ubuntu_linux Canonical 20.04 (including) 20.04 (including)
Ubuntu_linux Canonical 20.10 (including) 20.10 (including)
Ubuntu_linux Canonical 21.04 (including) 21.04 (including)
Ubuntu_linux Canonical 21.10 (including) 21.10 (including)
Apport Ubuntu bionic *
Apport Ubuntu devel *
Apport Ubuntu esm-infra/xenial *
Apport Ubuntu focal *
Apport Ubuntu groovy *
Apport Ubuntu hirsute *
Apport Ubuntu impish *
Apport Ubuntu jammy *
Apport Ubuntu trusty *
Apport Ubuntu trusty/esm *
Apport 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