CVE-2018-18955

MEDIUM

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: 2019-04-16

Type: CWE-20

Risk Information

CVSS v2.0

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 v3.0

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