CVE-2018-18955 Privilege escalation in n/a

What is CVE-2018-18955?

CVE-2018-18955 is a high-severity vulnerability in Canonical Ubuntu Linux, published on 16 Nov 2018. It can only be exploited from the same machine or local network, with no action from the victim.

Official 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.

Weakness: CWE-863

Which versions are affected by CVE-2018-18955?

It affects 2 products.

Products include Canonical Ubuntu Linux, Linux kernel.

How do I fix CVE-2018-18955?

Apply the vendor's patch.

Is CVE-2018-18955 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2018-18955 exists.

Public exploit code: 1 Metasploit module, 7 Exploit-DB entries and 2 proofs of concept on GitHub.

Other vulnerabilities in Canonical Ubuntu Linux

• CVE-2020-11651 SaltStack Salt Authentication Bypass Exploited Critical 9.8
• CVE-2020-7247 OpenSMTPD Remote Code Execution Exploited Critical 9.8
• CVE-2019-16928 Exim Out-of-bounds Write Exploited Critical 9.8
• CVE-2018-6789 Exim Buffer Overflow Exploited Critical 9.8
• CVE-2015-2590 Oracle Java SE and Java SE Embedded Remote Code Execution Exploited Critical 9.8

All Canonical Ubuntu Linux vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as DEBIAN-CVE-2018-18955, GHSA-c6xj-3c77-g5rg, UBUNTU-CVE-2018-18955.