Auth bypass in Linux Kernel
CVE-2018-18955
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.
Vulnerability class: Broken Access Control
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.0 (High). Vector: CVSS:3.0/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.076 (94.4th percentile), scored .
Low probability of exploitation in the next 30 days, but still tracked. 94th percentile — 94.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.076 · newest: 0.076 · change: 0.000
Affected products
- Linux Kernel
- Canonical Ubuntu Linux — versions 16.04, 18.04, 18.10
Weakness classification (CWE)
Public proof-of-concept exploits
References
- github.com/torvalds/linux/commit/d2f007dbe7e4c9583eea6eb04d60001e85c6f1bd (Patch, Vendor Advisory)
- cdn.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.18.19 (Patch, Vendor Advisory)
- usn.ubuntu.com/3836-2/ (vendor-advisory, Third Party Advisory)
- usn.ubuntu.com/3835-1/ (vendor-advisory, Third Party Advisory)
- bugs.chromium.org/p/project-zero/issues/detail (Patch, Third Party Advisory)
- git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/ (Patch, Vendor Advisory)
- usn.ubuntu.com/3833-1/ (vendor-advisory, Third Party Advisory)
- usn.ubuntu.com/3832-1/ (vendor-advisory, Third Party Advisory)
- www.exploit-db.com/exploits/45915/ (Exploit, VDB Entry, Third Party Advisory, exploit)
- cdn.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.19.2 (Patch, Vendor Advisory)
Frequently asked questions
- What is CVE-2018-18955?
- CVE-2018-18955 is a high-severity vulnerability in Linux Kernel, classified under Incorrect Authorization. CVSS score: 7.0/10. Published 2018-11-16.
- How severe is CVE-2018-18955?
- High severity. CVSS v3 base score is 7.0 out of 10.
- Is CVE-2018-18955 known to be exploited?
- 42 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.