The KEYS subsystem in the Linux kernel through 4.13.7 mishandles use of add_key for a key that already exists but is uninstantiated, which allows local users to cause a denial of service (NULL pointer dereference and system crash) or possibly have unspecified other impact via a crafted system call.
https://access.redhat.com/errata/RHSA-2018:0654
https://bugzilla.redhat.com/show_bug.cgi?id=1498016
https://lists.debian.org/debian-lts-announce/2017/12/msg00004.html
https://marc.info/?t=150654188100001&r=1&w=2
https://marc.info/?t=150783958600011&r=1&w=2
https://usn.ubuntu.com/3798-1/
https://usn.ubuntu.com/3798-2/
https://www.mail-archive.com/[email protected]/msg1499828.html
Source: MITRE
Published: 2017-10-14
Updated: 2018-10-30
Type: CWE-476
Base Score: 4.9
Vector: AV:L/AC:L/Au:N/C:N/I:N/A:C
Impact Score: 6.9
Exploitability Score: 3.9
Severity: MEDIUM
Base Score: 5.5
Vector: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Impact Score: 3.6
Exploitability Score: 1.8
Severity: MEDIUM