CVE-2019-15794: Canonical Ubuntu Linux

Medium severity, CVSS 6.7. EPSS: 1.2% chance of exploitation in the next 30 days.

Overlayfs in the Linux kernel and shiftfs, a non-upstream patch to the Linux kernel included in the Ubuntu 5.0 and 5.3 kernel series, both replace vma->vm_file in their mmap handlers. On error the original value is not restored, and the reference is put for the file to which vm_file points. On upstream kernels this is not an issue, as no callers dereference vm_file following after call_mmap() returns an error. However, the aufs patchs change mmap_region() to replace the fput() using a local variable with vma_fput(), which will fput() vm_file, leading to a refcount underflow.

Affected products

• Canonical Ubuntu Linux: version 18.04 only; version 19.10 only
• Linux Linux Kernel: version 5.0 only; version 5.3 only

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