FS#57527 - [shadow] newgidmap is setuid and allows an unprivileged user to be placed in a user namespace where

Attached to Project: Arch Linux
Opened by Karol Babioch (johnpatcher) - Friday, 16 February 2018, 08:46 GMT
Last edited by Dave Reisner (falconindy) - Saturday, 05 January 2019, 16:14 GMT
Task Type Bug Report
Category Security
Status Closed
Assigned To Dave Reisner (falconindy)
Levente Polyak (anthraxx)
Architecture All
Severity High
Priority Normal
Reported Version
Due in Version Undecided
Due Date Undecided
Percent Complete 100%
Votes 1
Private No

Details

CVE-2018-7169

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:
http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2018-7169
http://www.cvedetails.com/cve/CVE-2018-7169/
https://bugs.launchpad.net/ubuntu/+source/shadow/+bug/1729357

Fix:
https://github.com/shadow-maint/shadow/pull/97
This task depends upon

Closed by  Dave Reisner (falconindy)
Saturday, 05 January 2019, 16:14 GMT
Reason for closing:  Fixed
Additional comments about closing:  shadow-4.6-1

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