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.
CVE-2018-18955 - High Severity Vulnerability
The Linux Kernel
Library home page: https://mirrors.edge.kernel.org/pub/linux/kernel/v4.x/?wsslib=linux
Found in HEAD commit: 5efa23eac0f04571d486a6f7706fccc426b46cac
Found in base branch: master
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.
Publish Date: 2018-11-16
URL: CVE-2018-18955
Base Score Metrics: - Exploitability Metrics: - Attack Vector: Local - Attack Complexity: High - Privileges Required: Low - User Interaction: None - Scope: Unchanged - Impact Metrics: - Confidentiality Impact: High - Integrity Impact: High - Availability Impact: High
For more information on CVSS3 Scores, click here.Type: Upgrade version
Origin: https://nvd.nist.gov/vuln/detail/CVE-2018-18955
Release Date: 2018-11-16
Fix Resolution: linux-yocto - 5.4.20+gitAUTOINC+c11911d4d1_f4d7dbafb1,4.8.26+gitAUTOINC+1c60e003c7_27efc3ba68
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