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.
https://www.openwall.com/lists/oss-security/2019/06/11/2
https://www.debian.org/security/2019/dsa-4462
https://usn.ubuntu.com/4015-2/
https://usn.ubuntu.com/4015-1/
https://security.gentoo.org/glsa/201909-08
https://seclists.org/bugtraq/2019/Jun/16
https://lists.debian.org/debian-lts-announce/2019/06/msg00005.html
https://access.redhat.com/errata/RHSA-2019:3707
https://access.redhat.com/errata/RHSA-2019:2870
https://access.redhat.com/errata/RHSA-2019:2868
https://access.redhat.com/errata/RHSA-2019:1726
http://www.securityfocus.com/bid/108751
http://www.openwall.com/lists/oss-security/2019/06/11/2
http://lists.opensuse.org/opensuse-security-announce/2019-07/msg00026.html
http://lists.opensuse.org/opensuse-security-announce/2019-06/msg00092.html
http://lists.opensuse.org/opensuse-security-announce/2019-06/msg00059.html