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cis-ubuntu2004-v300-1-1-2-4-3

DevOps & Security
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Ensure nosuid option set on /var partition

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Source SKILL.md: https://github.com/CyberStrikeus/CyberStrike/blob/HEAD/.cyberstrike/skill/CIS_benchmarks/Operating_Systems/Ubuntu/CIS_Ubuntu_Linux_20.04_LTS_Benchmark_v3.0.0/cis-ubuntu2004-v300-1-1-2-4-3/SKILL.md

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Ensure nosuid option set on /var partition

Profile

Level 1 - Server, Level 1 - Workstation, Assessment: Automated

Description

The nosuid mount option specifies that the filesystem cannot contain setuid files.

Rationale

Since the /var filesystem is only intended for variable files such as logs, set this option to ensure that users cannot create setuid files in /var.

Audit Procedure

Command Line

  • IF - a separate partition exists for /var, verify that the nosuid option is set. Run the following command to verify that the nosuid mount option is set. Example:
# findmnt -kn /var | grep -v nosuid

Nothing should be returned

Expected Result

Nothing should be returned

Remediation

Command Line

  • IF - a separate partition exists for /var. Edit the /etc/fstab file and add nosuid to the fourth field (mounting options) for the /var partition. Example:
<device> /var   <fstype>   defaults,rw,nosuid,nodev,relatime   0 0

Run the following command to remount /var with the configured options:

# mount -o remount /var

Default Value

Not configured by default.

References

  1. See the fstab(5) manual page for more information.
  2. NIST SP 800-53 Rev. 5: AC-3, MP-2

CIS Controls

v8 - 3.3 Configure Data Access Control Lists (IG 1, IG 2, IG 3) v7 - 14.6 Protect Information through Access Control Lists (IG 1, IG 2, IG 3)

MITRE ATT&CK Mappings: T1548, T1548.001 | TA0005 | M1022