An assertion failure in dbus-daemon when a privileged Monitoring connection (dbus-monitor, busctl monitor, gdbus monitor or similar) is active, and a message from the bus driver cannot be delivered to a client connection due to <deny> rules or outgoing message quota. This is a denial of service if triggered maliciously by a local attacker

In other words, if a privileged user with control over the dbus-daemon is using the org.freedesktop.DBus.Monitoring interface to monitor message bus traffic, then an unprivileged user with the ability to connect to the same dbus-daemon can cause a dbus-daemon crash under some circumstances.

Vulnerable versions:

1.15.x before 1.15.6 1.14.x before 1.14.8 1.12.x before 1.12.28 most end-of-life versions since 1.9.x

Fixed versions:

all since 1.15.6 1.14.x since 1.14.8 1.12.x since 1.12.28

Not vulnerable: end-of-life versions 1.8.x or older do not contain the affected code path.

https://gitlab.freedesktop.org/dbus/dbus/-/issues/457 https://www.mail-archive.com/debian-bugs-dist@lists.debian.org/msg1908636.html

A flaw was discovered in dbus where the implementation of DBUSCOOKIESHA1 is susceptible to a symbolic link attack. A malicious client with write access to its own home directory could manipulate a ~/.dbus-keyrings symlink to cause the DBusServer to read and write in unintended locations. This could result in authentication bypass.