CVE-2018-6557 Insecure temporary file use in base-files
A local attacker can exploit insecure temporary file handling in the MOTD script to cause denial of service or escalate privileges if symlink restrictions are disabled.
- 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-2018-6557?
CVE-2018-6557 is a high-severity path traversal vulnerability in Canonical Ubuntu Linux, published on 21 Aug 2018. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
The MOTD update script in the base-files package in Ubuntu 18.04 LTS before 10.1ubuntu2.2, and Ubuntu 18.10 before 10.1ubuntu6 incorrectly handled temporary files. A local attacker could use this issue to cause a denial of service, or possibly escalate privileges if kernel symlink restrictions were disabled.
Weakness: CWE-59
Which versions are affected by CVE-2018-6557?
It affects 2 products.
Products include Base-Files Project Base-Files, Canonical Ubuntu Linux.
How do I fix CVE-2018-6557?
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-2018-6557 being exploited?
There is no known exploitation of CVE-2018-6557 in the wild and no public exploit code.
Sources
Also known as GHSA-vfrm-87wr-xvjf, UBUNTU-CVE-2018-6557, USN-3748-1.