CVE-2020-8831 World writable root owned lock file created in user controllable location
An attacker can exploit a symlink vulnerability in Apport's lock file creation to escalate privileges on Ubuntu systems.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2020-8831?
CVE-2020-8831 is a medium-severity path traversal vulnerability in Canonical Ubuntu Linux, published on 22 Apr 2020. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
Apport creates a world writable lock file with root ownership in the world writable /var/lock/apport directory. If the apport/ directory does not exist (this is not uncommon as /var/lock is a tmpfs), it will create the directory, otherwise it will simply continue execution using the existing directory. This allows for a symlink attack if an attacker were to create a symlink at /var/lock/apport, changing apport's lock file location. This file could then be used to escalate privileges, for example. Fixed in versions 2.20.1-0ubuntu2.23, 2.20.9-0ubuntu7.14, 2.20.11-0ubuntu8.8 and 2.20.11-0ubuntu22.
Which versions are affected by CVE-2020-8831?
It affects 2 products.
Products include Apport Project Apport, Canonical Ubuntu Linux.
How do I fix CVE-2020-8831?
Apply the vendor's patch.
Upgrade, and resolve every user-supplied path against an allowed base folder before opening it. More about Path traversal.
Is CVE-2020-8831 being exploited?
There is no known exploitation of CVE-2020-8831 in the wild and no public exploit code.
Other vulnerabilities in Canonical Ubuntu Linux
Sources
Also known as GHSA-33w2-prhc-2q89, UBUNTU-CVE-2020-8831.