| Name | CVE-2018-18955 |
| 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. |
| Source | CVE (at NVD; CERT, LWN, oss-sec, fulldisc, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more) |
Vulnerable and fixed packages
The table below lists information on source packages.
| Source Package | Release | Version | Status |
|---|
| linux (PTS) | buster | 4.19.249-2 | fixed |
| buster (security) | 4.19.289-2 | fixed |
| bullseye | 5.10.197-1 | fixed |
| bullseye (security) | 5.10.191-1 | fixed |
| bookworm | 6.1.55-1 | fixed |
| bookworm (security) | 6.1.52-1 | fixed |
| trixie | 6.5.10-1 | fixed |
| sid | 6.5.13-1 | fixed |
The information below is based on the following data on fixed versions.
| Package | Type | Release | Fixed Version | Urgency | Origin | Debian Bugs |
|---|
| linux | source | jessie | (not affected) | | | |
| linux | source | stretch | (not affected) | | | |
| linux | source | (unstable) | 4.18.20-1 | | | |
Notes
[stretch] - linux <not-affected> (Introduced in 4.15-rc1)
[jessie] - linux <not-affected> (Introduced in 4.15-rc1)
https://git.kernel.org/linus/d2f007dbe7e4c9583eea6eb04d60001e85c6f1bd
Introduced in https://git.kernel.org/linus/6397fac4915a
https://bugs.chromium.org/p/project-zero/issues/detail?id=1712