CVE-2019-15791
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.
Does this matter?
A public exploit is published in Exploit-DB (verified) and the impact is high, while EPSS rates exploitation at 1.3%. Anyone can run this; patch or mitigate before the next change window and check exposed instances for signs of use.
Description
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.
- CVSS 3.1
- 7.8 HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- EPSS
- 1.32% probability · 71th percentile
- Public exploits
- 1 in Exploit-DB · verified · first 20 November 2019
- CISA KEV
- Not listed
- Weakness
- CWE-672, CWE-191
- Affected
- linux/linux kernel · canonical/ubuntu linux
- Source
- security@ubuntu.com
EPSS 1.3% since 27 October 2026; no change recorded yet. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
Public exploits (1)
Entries in Exploit-DB that cite this CVE. Links go to the Exploit-DB page and to the file in the public repository; nothing is hosted here. A verified tick means the Exploit-DB team confirmed the exploit works against the stated version.
References
- https://git.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/eoan/commit/?id=601a64857b3d7040ca15c39c929e6b9db3373ec1Mailing List, Patch, Third Party Advisory
- https://usn.ubuntu.com/usn/usn-4183-1Third Party Advisory
- https://usn.ubuntu.com/usn/usn-4184-1Third Party Advisory
- https://git.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/eoan/commit/?id=601a64857b3d7040ca15c39c929e6b9db3373ec1Mailing List, Patch, Third Party Advisory
- https://usn.ubuntu.com/usn/usn-4183-1Third Party Advisory
- https://usn.ubuntu.com/usn/usn-4184-1Third Party Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.