{"cve":"CVE-2018-18955","nvd":{"published":"2018-11-16T20:29:00.233","modified":"2026-06-17T01:48:10.833","status":"Modified","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.","cvss_v4":null,"cvss_v3":{"version":"3.0","vector":"CVSS:3.0/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H","score":7.0},"cwes":["CWE-863"],"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"],"products":["canonical:ubuntu_linux","linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-19T20:53:59.789560037+00:00"},"epss":{"cve":"CVE-2018-18955","score":0.07611,"percentile":0.94553,"date":"2026-10-31"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}