CVE Vulnerabilities

CVE-2019-12749

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

Published: Jun 11, 2019 | Modified: Nov 07, 2023
CVSS 3.x
7.1
HIGH
Source:
NVD
CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
CVSS 2.x
3.6 LOW
AV:L/AC:L/Au:N/C:P/I:P/A:N
RedHat/V2
RedHat/V3
Ubuntu

dbus before 1.10.28, 1.12.x before 1.12.16, and 1.13.x before 1.13.12, as used in DBusServer in Canonical Upstart in Ubuntu 14.04 (and in some, less common, uses of dbus-daemon), allows cookie spoofing because of symlink mishandling in the reference implementation of DBUS_COOKIE_SHA1 in the libdbus library. (This only affects the DBUS_COOKIE_SHA1 authentication mechanism.) A malicious client with write access to its own home directory could manipulate a ~/.dbus-keyrings symlink to cause a DBusServer with a different uid to read and write in unintended locations. In the worst case, this could result in the DBusServer reusing a cookie that is known to the malicious client, and treating that cookie as evidence that a subsequent client connection came from an attacker-chosen uid, allowing authentication bypass.

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
Dbus Freedesktop 1.13.0 *
Dbus Freedesktop 1.12.0 *
Dbus Freedesktop * *

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