CVE-2018-18955

high
New! CVE Severity Now Using CVSS v3

The calculated severity for CVEs has been updated to use CVSS v3 by default. CVEs that do not have a CVSS v3 score will fall back CVSS v2 for calculating severity. Severity display preferences can be toggled in the settings dropdown.

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.

References

http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=d2f007dbe7e4c9583eea6eb04d60001e85c6f1bd

http://www.securityfocus.com/bid/105941

https://bugs.chromium.org/p/project-zero/issues/detail?id=1712

https://cdn.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.18.19

https://cdn.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.19.2

https://github.com/torvalds/linux/commit/d2f007dbe7e4c9583eea6eb04d60001e85c6f1bd

https://security.netapp.com/advisory/ntap-20190416-0003/

https://support.f5.com/csp/article/K39103040

https://usn.ubuntu.com/3832-1/

https://usn.ubuntu.com/3833-1/

https://usn.ubuntu.com/3835-1/

https://usn.ubuntu.com/3836-1/

https://usn.ubuntu.com/3836-2/

https://www.exploit-db.com/exploits/45886/

https://www.exploit-db.com/exploits/45915/

Details

Source: MITRE

Published: 2018-11-16

Updated: 2020-08-24

Type: CWE-863

Risk Information

CVSS v2

Base Score: 4.4

Vector: AV:L/AC:M/Au:N/C:P/I:P/A:P

Impact Score: 6.4

Exploitability Score: 3.4

Severity: MEDIUM

CVSS v3

Base Score: 7

Vector: CVSS:3.0/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

Impact Score: 5.9

Exploitability Score: 1

Severity: HIGH

Tenable Plugins

View all (5 total)

IDNameProductFamilySeverity
119340Ubuntu 16.04 LTS : linux-hwe, linux-gcp vulnerabilities (USN-3836-2)NessusUbuntu Local Security Checks
high
119339Ubuntu 18.04 LTS : linux, linux-gcp, linux-kvm, linux-raspi2 vulnerabilities (USN-3836-1)NessusUbuntu Local Security Checks
high
119338Ubuntu 18.10 : linux, linux-gcp, linux-kvm, linux-raspi2 vulnerabilities (USN-3835-1)NessusUbuntu Local Security Checks
high
119303Ubuntu 18.04 LTS : Linux kernel (AWS) vulnerabilities (USN-3833-1)NessusUbuntu Local Security Checks
high
119302Ubuntu 18.10 : Linux kernel (AWS) vulnerabilities (USN-3832-1)NessusUbuntu Local Security Checks
high