UBUNTU-CVE-2018-7169

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UBUNTU-CVE-2018-7169

Summary:

Details: An issue was discovered in shadow 4.5. newgidmap (in shadow-utils) is setuid and allows an unprivileged user to be placed in a user namespace where setgroups(2) is permitted. This allows an attacker to remove themselves from a supplementary group, which may allow access to certain filesystem paths if the administrator has used "group blacklisting" (e.g., chmod g-rwx) to restrict access to paths. This flaw effectively reverts a security feature in the kernel (in particular, the /proc/self/setgroups knob) to prevent this sort of privilege escalation.

References: https://ubuntu.com/security/CVE-2018-7169, https://github.com/shadow-maint/shadow/pull/97, https://ubuntu.com/security/notices/USN-5254-1, https://www.cve.org/CVERecord?id=CVE-2018-7169