CVE-2022-28655

What it actually does

The is_closing_session() function in apport permits local users to instantiate arbitrary TCP DBus connections, bypassing intended local authorization restrictions on DBus access.

Why it matters to the business

Local attackers on affected Ubuntu systems can interact with DBus services in ways that should be blocked, potentially leading to unauthorized configuration changes, service manipulation, or further privilege escalation with resulting system instability or data exposure.

How an attack unfolds

An attacker with a local shell invokes the vulnerable is_closing_session() entry point to open a TCP DBus connection to a target service, then issues method calls or signals that the service would normally reject from an untrusted local user.

How to fix it

Upgrade the apport package to the latest available version from the distribution that contains the corrected is_closing_session() implementation; apply all pending Ubuntu security updates and monitor apport release announcements for backports.

How to confirm the fix worked

Confirm the installed apport package version is newer than the vulnerable release, review the source for the patched is_closing_session() logic, and test that local users can no longer create unauthorized TCP DBus connections.

Typical attack path

1. Obtain local shell access on an affected system
2. Execute code or commands that call is_closing_session()
3. Establish an arbitrary TCP DBus connection
4. Interact with restricted DBus services to alter system state

How to detect it

Review system and apport logs for unexpected DBus TCP connection attempts originating from user processes; correlate with process creation events around the time of the vulnerable function invocation.

What your security team should do

• Prioritize patching apport on all Ubuntu systems within the next maintenance window
• Audit local user accounts and restrict unnecessary DBus access where possible
• Enable enhanced logging for DBus connections to detect anomalous TCP sessions