CVE-2018-18955
Description
A flaw was found in the Linux kernel where map_write() in kernel/user_namespace.c allows privilege escalation as it mishandles nested user namespaces with more than 5 UID or GID ranges. An unprivileged user with CAP_SYS_ADMIN in an affected user namespace can bypass access controls on resources outside the namespace. This is possible because a user/group id transformation takes place properly for the namespaced-to-kernel direction but not for the kernel-to-namespaced direction.
Statement
This issue does not affect the Linux kernel versions as shipped with Red Hat Enterprise Linux 5, 6 and 7 because they did not include the commit that introduced this issue.
This issue does not affect Red Hat Enterprise Linux 8 because the fix for this issue has not been included since the Red Hat Enterprise Linux 8 release.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 7.8 | 7 | N/A |
| Attack Vector | Local | Local | N/A |
| Attack Complexity | High | High | N/A |
| Privileges Required | Low | Low | N/A |
| User Interaction | None | None | N/A |
| Scope | Changed | Unchanged | N/A |
| Confidentiality | High | High | N/A |
| Integrity Impact | High | High | N/A |
| Availability Impact | High | High | N/A |
Vector
Red Hat: CVSS:3.0/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H
NVD: CVSS:3.0/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
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