CVE-2018-18955
HIGH7.0EPSS 9.6%Published: 11/16/2018Modified: 4/28/2026
Description
In the Linux kernel 4.15.x through 4.19.x before 4.19.2, map_write() in kernel/user_namespace.c allows privilege escalation because it mishandles nested user namespaces with more than 5 UID or GID ranges. A user who has CAP_SYS_ADMIN in an affected user namespace can bypass access controls on resources outside the namespace, as demonstrated by reading /etc/shadow. This occurs because an ID transformation takes place properly for the namespaced-to-kernel direction but not for the kernel-to-namespaced direction.
Affected packages (1)
- Debian/linuxfrom 0, < 4.18.20-1
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 3.1 | HIGH7.0 | CVSS:3.0/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H |