CVE-2019-19377

A flaw was found in the Linux kernel's implementation of the BTRFS file system. A local attacker, with the ability to mount a file system, can create a use-after-free memory fault after the file system has been unmounted. This may lead to memory corruption or privilege escalation.

This flaw is rated as moderate, the attacker would need to have physical access or permission to mount/write to a filesystem to abuse this. If they can write to a block device they can already do other evil things, like make a setuid binary etc.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

As the btrfs module will be auto-loaded when required, its use can be disabled by preventing the module from loading with the following instructions:

echo "install btrfs /bin/true" >> /etc/modprobe.d/disable-btrfs.conf

The system will need to be restarted if the BTRFS modules are loaded. In most circumstances, the CIFS kernel modules will be unable to be unloaded while any network interfaces are active and the protocol is in use.

If the system requires this module to work correctly (as a filesytem required to run), this mitigation may not be suitable.

If you need further assistance, see KCS article https://access.redhat.com/solutions/41278 or contact Red Hat Global Support Services.