SV-257855r1044936: RHEL 9 must prevent code from being executed on file systems that are imported via Network File System (NFS). | Red Hat Enterprise Linux 9 STIG SCAP Benchmark

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Assessment Title

Rule Text

RHEL 9 must prevent code from being executed on file systems that are imported via Network File System (NFS).

Description

Discussion Text

The "noexec" mount option causes the system not to execute binary files. This option must be used for mounting any file system not containing approved binary as they may be incompatible. Executing files from untrusted file systems increases the opportunity for nonprivileged users to attain unauthorized administrative access.

How this relates to the STIG checklist: STIG vs SCAP benchmark.

IA Controls

NIST SP 800-53

Not mappedCCI-000366

References

DPMS Target Red Hat Enterprise Linux 9 DISA DPMS Target Red Hat Enterprise Linux 9 5551

Checks

DISA STIG (Manual Reference)

Note: If no NFS mounts are configured, this requirement is Not Applicable.

Verify RHEL 9 has the "noexec" option configured for all NFS mounts with the following command:

$ grep nfs /etc/fstab

192.168.22.2:/mnt/export /data nfs4 rw,nosuid,nodev,noexec,sync,soft,sec=krb5:krb5i:krb5p

If the system is mounting file systems via NFS and the "noexec" option is missing, this is a finding.

SCC Automation Reference

The reconstructed evaluation script behind this rule's OVAL check(s) — every module a compound check combines, with this rule's own concrete values and DISA's SCC tool's real per-module mechanism curated from static teardown of SCC releases.

#!/bin/bash
# Reconstructed from oval:mil.disa.stig.rhel9os:def:257855
# RHEL 9  must prevent code from being executed on file systems that are imported via Network File System (NFS).
# Per-module read mechanism curated from static teardown of DISA's SCC tool
# (SCAP Compliance Checker) -- see the SCC Automation Reference above.

# remote nfs filesystems in /etc/fstab have noexec
# textfilecontent54_object (textfilecontent54_test)
test_1() {
  (sed -En 's/^\s*[^#\s][^\s]*\s+[^\s]+\s+nfs[^\s]*\s+([^\s]+)/\1/p' '/etc/fstab') | grep -Pq '(^|,)noexec(,|$)'
}

if test_1; then
  echo "PASS"
else
  echo "FAIL"
fi

Remediation

Update each NFS mounted file system to use the "noexec" option on file systems that are being imported via NFS.