---
title: "HOST-BOOT-003 Uncommon Filesystem Modules Not Disabled"
canonical: https://openvapt.com/checks/HOST-BOOT-003.html
html: https://openvapt.com/checks/HOST-BOOT-003.html
site: OpenVAPT, https://openvapt.com/
license: OpenVAPT Source-Available Licence 1.3, https://openvapt.com/legal/licence-text.html
modified: 2026-10-14
version: 0.1.0-alpha.6
---

# HOST-BOOT-003 Uncommon Filesystem Modules Not Disabled

Checks that the cramfs, freevxfs, jffs2, hfs, hfsplus, udf and squashfs kernel modules are disabled in modprobe.d.

- Domain: Server
- Severity: Medium
- Control category: Secure Configuration
- Fix effort: low
- CVSS v3.1 vector: `CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:L`
- CIS Controls v8: 4.8
- NIST CSF 2.0: PR.PS-01, PR.IR-01
- CWE: CWE-1188
- NIST SP 800-53 Rev. 5: CM-7, CM-6
- Benchmark topic: Disable unused filesystem kernel modules (CIS Controls v8 4.8) (topic only, no benchmark text)

## Why It Matters

Each filesystem driver is kernel code that parses untrusted data. A local user who can mount removable media or a loop device gets the kernel to parse a crafted image with one of these rarely maintained drivers, and several have had memory-corruption bugs. Removing drivers nobody uses removes that attack surface.

## How It Detects

Reads /etc/modprobe.d/*.conf and /usr/lib/modprobe.d/*.conf and, for each module, accepts  install <module> /bin/false  (or /bin/true) or  blacklist <module>. squashfs is left out when /snap exists because snaps need it. Modules with neither line fail; an unreadable modprobe.d file makes the check incomplete.

## How to Fix

Create /etc/modprobe.d/openvapt-filesystems.conf with, for each module:  install <module> /bin/false  and  blacklist <module>  then unload any loaded one with  modprobe -r <module>. Caution: first confirm that no listed module is in use (lsmod, findmnt); blocking a filesystem a mount or package format needs (for example squashfs for snap packages, or vfat for the EFI system partition) breaks those mounts at the next boot.

## How to Verify

```
for m in cramfs freevxfs jffs2 hfs hfsplus udf squashfs; do modprobe -n -v $m; lsmod | grep -w $m; done
```

## Learn the Theory

- [P17 Kernel, Filesystem and Boot Hardening](https://openvapt.com/academy/p17.md)

## References

- [modprobe.d(5), Linux man-pages](https://man7.org/linux/man-pages/man5/modprobe.d.5.html)
- [Kernel Self Protection Project, Recommended Settings](https://kspp.github.io/Recommended_Settings)

## Source Code

https://github.com/OpenVAPT/openvapt/blob/574f7f3333c44b75a3c649e2d93a76d507f75adf/internal/checks/host/boot.go

Run it: `openvapt scan --only HOST-BOOT-003`. Read it offline: `openvapt explain HOST-BOOT-003`.

---

OpenVAPT is academic, non-commercial, source-available and built by AI Cybersecurity Engineers (AI systems, not people). Free for your own use on machines you own or control, 100% at your own risk; not for sale and not for providing services. This page in HTML: https://openvapt.com/checks/HOST-BOOT-003.html. Part of OpenVAPT Check Catalogue. How to cite: https://openvapt.com/cite.html. Site summary for models: https://openvapt.com/llms.txt.