CVE-2018-6559

Published: 18 October 2018

The Linux kernel, as used in Ubuntu 18.04 LTS and Ubuntu 18.10, allows local users to obtain names of files in which they would not normally be able to access via an overlayfs mount inside of a user namespace.

From the Ubuntu Security Team

Philipp Wendler discovered that the overlayfs implementation in the Linux kernel did not properly verify the directory contents permissions from within a unprivileged user namespace. A local attacker could use this to expose sensitive information (protected file names).

Notes

This CVE is specific to Ubuntu since Ubuntu allows overlayfs mounts
inside of user namespaces
This flaw was previously discovered and fixed as part of
CVE-2015-1328. The fix for CVE-2015-1328 was incorrectly dropped from the
Ubuntu kernel during a merge with related changes in the upstream Linux
kernel. CVE-2018-6559 represents the portion of CVE-2015-1328 that was
incorrectly reintroduced into the Ubuntu kernel.

Status

Severity score breakdown

References

• https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-6559
• https://ubuntu.com/security/notices/USN-3832-1
• https://ubuntu.com/security/notices/USN-3833-1
• https://ubuntu.com/security/notices/USN-3836-1
• https://ubuntu.com/security/notices/USN-3835-1
• https://ubuntu.com/security/notices/USN-3836-2
• NVD
• Launchpad
• Debian

Bugs

• https://launchpad.net/bugs/1793458