CVE-2018-18955

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    CVE-2018-18955

    Published: 16 Nov 2018Last Modified: 15 Mar 2026

    Summary:

    Details: 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.

    References: https://support.f5.com/csp/article/K39103040, https://security.netapp.com/advisory/ntap-20190416-0003/, https://usn.ubuntu.com/3836-2/, http://www.securityfocus.com/bid/105941, https://usn.ubuntu.com/3832-1/, https://usn.ubuntu.com/3833-1/, https://usn.ubuntu.com/3835-1/, https://usn.ubuntu.com/3836-1/, https://cdn.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.19.2, https://github.com/torvalds/linux/commit/d2f007dbe7e4c9583eea6eb04d60001e85c6f1bd, https://www.exploit-db.com/exploits/45886/, https://bugs.chromium.org/p/project-zero/issues/detail?id=1712, http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=d2f007dbe7e4c9583eea6eb04d60001e85c6f1bd, https://cdn.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.18.19, https://www.exploit-db.com/exploits/45915/

    Affected packages

    Package

    Name:

    Purl:

    Affected ranges

    Type: N/A

    Events:

    Introduced- None
    Fixed -None

    Affected versions

    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High