CVE Vulnerabilities

CVE-2019-12779

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

Published: Jun 07, 2019 | Modified: Jul 03, 2021
CVSS 3.x
7.1
HIGH
Source:
NVD
CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H
CVSS 2.x
6.6 MEDIUM
AV:L/AC:L/Au:N/C:N/I:C/A:C
RedHat/V2
RedHat/V3
6.5 MODERATE
CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:N
Ubuntu
LOW

libqb before 1.0.5 allows local users to overwrite arbitrary files via a symlink attack, because it uses predictable filenames (under /dev/shm and /tmp) without O_EXCL.

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
Libqb Clusterlabs * 1.0.5 (excluding)
Red Hat Enterprise Linux 7 RedHat libqb-0:1.0.1-9.el7 *
Red Hat Enterprise Linux 8 RedHat libqb-0:1.0.3-10.el8 *
Libqb Ubuntu bionic *
Libqb Ubuntu cosmic *
Libqb Ubuntu disco *
Libqb Ubuntu esm-infra/bionic *
Libqb Ubuntu esm-infra/xenial *
Libqb Ubuntu trusty *
Libqb Ubuntu trusty/esm *
Libqb Ubuntu upstream *
Libqb 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