CVE-2018-18955
HIGHEPSS 94th pctlDescription
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.
How to fix
TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works
Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3 Vector
Exploitability
Impact
CVSS:3.0/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Exploit Intelligence
High risk: more likely to be exploited than 94% of all known CVEs.
References
Related Vulnerabilities
Other CWE-863 (Incorrect Authorization) vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2023-22518 | Critical | 9.8 | 100% | KEV + Ransom | Fix |
| CVE-2023-38035 | Critical | 9.8 | 100% | KEV + Ransom | - |
| CVE-2022-46169 | Critical | 9.8 | 100% | KEV | Fix |
| CVE-2024-38856 | Critical | 9.8 | 99% | KEV | Fix |
| CVE-2025-29927 | Critical | 9.1 | 99% | - | Fix |
| CVE-2020-36289 | Medium | 5.3 | 99% | - | Fix |
Common questions
How do I fix CVE-2018-18955?
Published advisories record a fix for 14 affected products. The "How to fix" section on this page lists the fixed version and source advisory for each one, so apply the entry matching what you actually run.
Is CVE-2018-18955 being actively exploited?
Not that we know of. CVE-2018-18955 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 7.6% is the estimated probability that it will be exploited in the next 30 days. That is higher than 94% of all scored CVEs.
How severe is CVE-2018-18955?
CVE-2018-18955 has a CVSS v3 base score of 7.0, rated high. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2018-18955 affect?
Published advisories record a fix for linux (Debian), linux (Ubuntu), linux-aws (Ubuntu), linux-gcp (Ubuntu), and 10 more. Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2024-11-21.