Setup in Fedora and Red Hat Enterprise Linux added /sbin/nologin and /usr/sbin/nologin to /etc/shells. This violates security assumptions made by pam_shells and some daemons which allow access based on a user's shell being listed in /etc/shells. Under some circumstances, users which had their shell changed to /sbin/nologin could still access the system.
Find out more about CVE-2018-1113 from the MITRE CVE dictionary dictionary and NIST NVD.
Preventing a user from accessing the system without deleting their account is not a simple matter. For utmost security, the account should be deleted. Short of this, we recommend a three-pronged approach:
* change the user's login shell to a harmless command that is not in "/etc/shells" (for example "/bin/false") to prevent commands being run on their behalf
* lock the user's password with "usermod -L" to prevent authentication with pam services
* prevent access to the user's home directory with "chmod 0" or "chown root" and "chmod 700" to prevent authentication with ssh keys etc
| CVSS3 Base Score | 4.8 |
|---|---|
| CVSS3 Base Metrics | CVSS:3.0/AV:L/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:L |
| Attack Vector | Local |
| Attack Complexity | Low |
| Privileges Required | Low |
| User Interaction | Required |
| Scope | Unchanged |
| Confidentiality | Low |
| Integrity Impact | Low |
| Availability Impact | Low |
| Platform | Errata | Release Date |
|---|---|---|
| Red Hat Enterprise Linux 7 (setup) | RHSA-2018:3249 | 2018-10-30 |
| Platform | Package | State |
|---|---|---|
| Red Hat Enterprise Linux 6 | setup | Affected |
| Red Hat Enterprise Linux 5 | setup | Will not fix |
Vulmon