---
title: "HOST-FS-018 Kernel Symbol Map or Initial RAM Disk Readable by Others"
canonical: https://openvapt.com/checks/HOST-FS-018.html
html: https://openvapt.com/checks/HOST-FS-018.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-FS-018 Kernel Symbol Map or Initial RAM Disk Readable by Others

Checks that /boot/System.map-* and the initial RAM disk images are not readable by every user.

- Domain: Server
- Severity: Low
- Control category: Information Exposure
- Fix effort: low
- CVSS v3.1 vector: `CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N`
- CIS Controls v8: 3.3
- NIST CSF 2.0: PR.AA-05, PR.DS-01
- CWE: CWE-497, CWE-732
- NIST SP 800-53 Rev. 5: AC-3, AC-6
- Benchmark topic: Boot file permissions (CIS Controls v8 3.3) (topic only, no benchmark text)

## Why It Matters

System.map lists every kernel symbol address, which defeats kptr_restrict and helps kernel exploits. An initial RAM disk can embed network credentials, disk-unlock key files or custom scripts that should not be world-readable.

## How It Detects

Stats /boot/System.map-*, /boot/initrd.img-*, /boot/initramfs-*.img and /boot/initrd-* (metadata only) and fails if any is readable by others. Skipped when none exist (for example inside a container).

## How to Fix

chmod 600 /boot/System.map-* /boot/initrd* /boot/initramfs*  and, on Debian family systems, set  UMASK=0077  in /etc/initramfs-tools/initramfs.conf so new images are created private.

## How to Verify

```
stat -c '%a %n' /boot/System.map-* /boot/initrd*
```

## Learn the Theory

- [P1 Linux Server Hardening](https://openvapt.com/academy/p1.md)
- [P17 Kernel, Filesystem and Boot Hardening](https://openvapt.com/academy/p17.md)

## References

- [Linux kernel documentation, /proc/sys/kernel](https://docs.kernel.org/admin-guide/sysctl/kernel.html)
- [NIST SP 800-123, Guide to General Server Security](https://csrc.nist.gov/pubs/sp/800/123/final)

## Source Code

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

Run it: `openvapt scan --only HOST-FS-018`. Read it offline: `openvapt explain HOST-FS-018`.

---

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