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cis-ubuntu1804-v220-1-1-4-4

DevOps & Security
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Ensure nosuid option set on /var/tmp 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_18.04_LTS_Benchmark_v2.2.0/cis-ubuntu1804-v220-1-1-4-4/SKILL.md

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Ensure nosuid option set on /var/tmp 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/tmp filesystem is only intended for temporary file storage, set this option to ensure that users cannot create setuid files in /var/tmp.

Impact

None noted.

Audit Procedure

Command Line

Verify that the nosuid option is set for the /var/tmp mount.

# findmnt -kn /var/tmp | grep nosuid

Expected Result

/var/tmp     /dev/sda3  ext4   rw,nosuid,nodev,noexec,relatime,seclabel

Remediation

Command Line

Edit the /etc/fstab file and add nosuid to the fourth field (mounting options) for the /var/tmp partition.

# Example:
# <device> /var/tmp   <fstype>   defaults,rw,nosuid,nodev,noexec,relatime   0 0

# Run the following command to remount /var/tmp with the configured options:
mount -o remount /var/tmp

Default Value

Not set 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, M1038