--- title: CVE-2018-18955 description: Ubuntu is an open source software operating system that runs from the desktop, to the cloud, to all your internet connected things. url: https://ubuntu.com/security/CVE-2018-18955 --- # CVE-2018-18955 Publication date 16 November 2018 Last updated 4 July 2026 --- Ubuntu priority **Medium** [Why this priority?](https://ubuntu.com/security/cves/about#priority ) ## Cvss 3 Severity Score **7.0 · High** [Score breakdown](https://ubuntu.com/security/CVE-2018-18955#impact-score) Toggle side navigation ## 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. ### From the Ubuntu Security Team Jann Horn discovered that the Linux kernel mishandles mapping UID or GID ranges inside nested user namespaces in some situations. A local attacker could use this to bypass access controls on resources outside the namespace. ## Status Show unmaintained releases | Package | Ubuntu Release | Status | | --- | --- | --- | | linux | 18.10 cosmic | Fixed 4.18.0-12.13 | | 18.04 LTS bionic | Fixed 4.15.0-42.45 | | 16.04 LTS xenial | Not affected | | 14.04 LTS trusty | Not affected | | linux-aws | 18.10 cosmic | Fixed 4.18.0-1006.7 | | 18.04 LTS bionic | Fixed 4.15.0-1029.30 | | 16.04 LTS xenial | Not affected | | 14.04 LTS trusty | Not affected | | linux-aws-hwe | 18.10 cosmic | Not in release | | 18.04 LTS bionic | Not in release | | 16.04 LTS xenial | Not affected | | 14.04 LTS trusty | Not in release | | linux-azure | 18.10 cosmic | Fixed 4.18.0-1006.6 | | 18.04 LTS bionic | Fixed 4.15.0-1035.36 | | 16.04 LTS xenial | Fixed 4.15.0-1035.36~16.04.1 | | 14.04 LTS trusty | Fixed 4.15.0-1035.36~14.04.2 | | linux-azure-edge | 18.10 cosmic | Not in release | | 18.04 LTS bionic | Fixed 4.15.0-1035.36 | | 16.04 LTS xenial | Fixed 4.15.0-1035.36~16.04.1 | | 14.04 LTS trusty | Not in release | | linux-euclid | 18.10 cosmic | Not in release | | 18.04 LTS bionic | Not in release | | 16.04 LTS xenial | Not in release | | 14.04 LTS trusty | Not in release | | linux-flo | 18.10 cosmic | Not in release | | 18.04 LTS bionic | Not in release | | 16.04 LTS xenial | Not in release | | 14.04 LTS trusty | Not in release | | linux-gcp | 18.10 cosmic | Fixed 4.18.0-1004.5 | | 18.04 LTS bionic | Fixed 4.15.0-1025.26 | | 16.04 LTS xenial | Fixed 4.15.0-1025.26~16.04.1 | | 14.04 LTS trusty | Not in release | | linux-gcp-edge | 18.10 cosmic | Not in release | | 18.04 LTS bionic | Not affected | | 16.04 LTS xenial | Not in release | | 14.04 LTS trusty | Not in release | | linux-gke | 18.10 cosmic | Not in release | | 18.04 LTS bionic | Not in release | | 16.04 LTS xenial | Ignored end of standard support | | 14.04 LTS trusty | Not in release | | linux-goldfish | 18.10 cosmic | Not in release | | 18.04 LTS bionic | Not in release | | 16.04 LTS xenial | Not in release | | 14.04 LTS trusty | Not in release | | linux-grouper | 18.10 cosmic | Not in release | | 18.04 LTS bionic | Not in release | | 16.04 LTS xenial | Not in release | | 14.04 LTS trusty | Not in release | | linux-hwe | 18.10 cosmic | Not in release | | 18.04 LTS bionic | Not affected | | 16.04 LTS xenial | Fixed 4.15.0-42.45~16.04.1 | | 14.04 LTS trusty | Not in release | | linux-hwe-edge | 18.10 cosmic | Not in release | | 18.04 LTS bionic | Not affected | | 16.04 LTS xenial | Fixed 4.15.0-42.45~16.04.1 | | 14.04 LTS trusty | Not in release | | linux-kvm | 18.10 cosmic | Fixed 4.18.0-1005.5 | | 18.04 LTS bionic | Fixed 4.15.0-1027.27 | | 16.04 LTS xenial | Not affected | | 14.04 LTS trusty | Not in release | | linux-lts-trusty | 18.10 cosmic | Not in release | | 18.04 LTS bionic | Not in release | | 16.04 LTS xenial | Not in release | | 14.04 LTS trusty | Not in release | | linux-lts-utopic | 18.10 cosmic | Not in release | | 18.04 LTS bionic | Not in release | | 16.04 LTS xenial | Not in release | | 14.04 LTS trusty | Not in release | | linux-lts-vivid | 18.10 cosmic | Not in release | | 18.04 LTS bionic | Not in release | | 16.04 LTS xenial | Not in release | | 14.04 LTS trusty | Not in release | | linux-lts-wily | 18.10 cosmic | Not in release | | 18.04 LTS bionic | Not in release | | 16.04 LTS xenial | Not in release | | 14.04 LTS trusty | Not in release | | linux-lts-xenial | 18.10 cosmic | Not in release | | 18.04 LTS bionic | Not in release | | 16.04 LTS xenial | Not in release | | 14.04 LTS trusty | Not affected | | linux-maguro | 18.10 cosmic | Not in release | | 18.04 LTS bionic | Not in release | | 16.04 LTS xenial | Not in release | | 14.04 LTS trusty | Not in release | | linux-mako | 18.10 cosmic | Not in release | | 18.04 LTS bionic | Not in release | | 16.04 LTS xenial | Not in release | | 14.04 LTS trusty | Not in release | | linux-manta | 18.10 cosmic | Not in release | | 18.04 LTS bionic | Not in release | | 16.04 LTS xenial | Not in release | | 14.04 LTS trusty | Not in release | | linux-oem | 18.10 cosmic | Fixed 4.15.0-1028.33 | | 18.04 LTS bionic | Fixed 4.15.0-1028.33 | | 16.04 LTS xenial | Ignored end of standard support, was needs-triage | | 14.04 LTS trusty | Not in release | | linux-oracle | 18.10 cosmic | Not affected | | 18.04 LTS bionic | Not affected | | 16.04 LTS xenial | Not affected | | 14.04 LTS trusty | Not in release | | linux-raspi2 | 18.10 cosmic | Fixed 4.18.0-1007.9 | | 18.04 LTS bionic | Fixed 4.15.0-1029.31 | | 16.04 LTS xenial | Not affected | | 14.04 LTS trusty | Not in release | | linux-snapdragon | 18.10 cosmic | Not in release | | 18.04 LTS bionic | Not affected | | 16.04 LTS xenial | Not affected | | 14.04 LTS trusty | Not in release | --- * [How can I get the fixes?](https://ubuntu.com/security/cves/about#security) * [What do statuses mean?](https://ubuntu.com/security/cves/about#statuses) * [Patch details](https://ubuntu.com/security/CVE-2018-18955#patch-details) ### Patch details For informational purposes only. We recommend not to cherry-pick updates. [How can I get the fixes?](https://ubuntu.com/security/cves/about#security) | Package | Patch details | | --- | --- | | linux | * Introduced by [6397fac](https://git.kernel.org/linus/6397fac4915ab3002dc15aae751455da1a852f25), fixed by [d2f007d](https://git.kernel.org/linus/d2f007dbe7e4c9583eea6eb04d60001e85c6f1bd) | ## Severity score breakdown CVSS version: CVSS v3.0 **Base score** 7.0 · High * Base metrics | Parameter | Value | | --- | --- | | Attack vector | Local | | Attack complexity | High | | Privileges required | Low | | User interaction | None | | Scope | Unchanged | | Confidentiality impact | High | | Integrity impact | High | | Availability impact | High | * Scores | Parameter | Value | | --- | --- | | Base score | 7.0 · High | | Exploitability score | - | | Impact score | - | **Vector:** CVSS:3.0/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H ## References * [MITRE](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-18955) * [NVD](https://nvd.nist.gov/vuln/detail/CVE-2018-18955) * [Launchpad](https://launchpad.net/bugs/cve/CVE-2018-18955) * [Debian](https://security-tracker.debian.org/tracker/CVE-2018-18955) ### Related Ubuntu Security Notices (USN) + [USN-3835-1](https://usn.ubuntu.com/USN-3835-1) + Linux kernel vulnerabilities + 3 December 2018 + [USN-3833-1](https://usn.ubuntu.com/USN-3833-1) + Linux kernel (AWS) vulnerabilities + 30 November 2018 + [USN-3836-1](https://usn.ubuntu.com/USN-3836-1) + Linux kernel vulnerabilities + 3 December 2018 + [USN-3836-2](https://usn.ubuntu.com/USN-3836-2) + Linux kernel (HWE) vulnerabilities + 4 December 2018 + [USN-3832-1](https://usn.ubuntu.com/USN-3832-1) + Linux kernel (AWS) vulnerabilities + 30 November 2018 ### Other references *