CVE-2019-12749

Impact:
Important
Public Date:
2019-06-11
CWE:
CWE-592
Bugzilla:
1719344: CVE-2019-12749 dbus: DBusServer DBUS_COOKIE_SHA1 authentication bypass

The MITRE CVE dictionary describes this issue as:

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.

Find out more about CVE-2019-12749 from the MITRE CVE dictionary dictionary and NIST NVD.

Statement

This flaw is mitigated by the fact that by default, the well-known system dbus-daemon (since 2003) and the well-known session dbus-daemon (in stable releases since dbus 1.10.0 in 2015) only accept the EXTERNAL authentication mechanism, and as a result will reject DBUS_COOKIE_SHA1 at an early stage, before manipulating cookies.

Red Hat Enterprise Linux 6 is affected by this flaw, which can be leveraged to achieve privilege escalation via upstart. This issue has been rated as having important impact for Red Hat Enterprise Linux 6.

Red Hat Enterprise Linux 7 and 8, both ship dbus >= 1.10 and therefore are affected by this flaw only when system or session dbus-daemons are used under non-standard configurations or by third party users of DBusServer. Red Hat Enterprise Linux 7 and 8 does not ship any affected DBusServer cosumer. However third party applications may be affected.

CVSS v3 metrics

CVSS3 Base Score 7
CVSS3 Base Metrics CVSS:3.0/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Attack Vector Local
Attack Complexity High
Privileges Required Low
User Interaction None
Scope Unchanged
Confidentiality High
Integrity Impact High
Availability Impact High

Red Hat Security Errata

Platform Errata Release Date
Red Hat Enterprise Linux 6 (dbus) RHSA-2019:1726 2019-07-10

Affected Packages State

Platform Package State
Red Hat Enterprise Linux 8 dbus Affected
Red Hat Enterprise Linux 7 dbus Affected
Red Hat Enterprise Linux 5 dbus Out of support scope
Unless explicitly stated as not affected, all previous versions of packages in any minor update stream of a product listed here should be assumed vulnerable, although may not have been subject to full analysis.

Acknowledgements

Red Hat would like to thank the D-Bus project for reporting this issue. Upstream acknowledges Joe Vennix (Apple Information Security) as the original reporter.

External References

Last Modified

CVE description copyright © 2017, The MITRE Corporation