CVE-2019-15791: Canonical Ubuntu Linux

High severity, CVSS 7.8. EPSS: 1.3% chance of exploitation in the next 30 days.

In shiftfs, a non-upstream patch to the Linux kernel included in the Ubuntu 5.0 and 5.3 kernel series, shiftfs_btrfs_ioctl_fd_replace() installs an fd referencing a file from the lower filesystem without taking an additional reference to that file. After the btrfs ioctl completes this fd is closed, which then puts a reference to that file, leading to a refcount underflow.

Affected products

• Canonical Ubuntu Linux: version 18.04 only; version 19.04 only
• Linux Linux Kernel: version 5.0 only; version 5.3 only

Published 2020-04-24. Last modified 2026-06-17.