---
title: "HOST-FS-019 Cron and At Not Restricted to Allowed Users"
canonical: https://openvapt.com/checks/HOST-FS-019.html
html: https://openvapt.com/checks/HOST-FS-019.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-019 Cron and At Not Restricted to Allowed Users

Checks that cron.allow and at.allow exist, are private to root, and that the deny lists are not relied upon instead.

- Domain: Server
- Severity: Low
- Control category: Access Control
- Fix effort: low
- CVSS v3.1 vector: `CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N`
- CIS Controls v8: 4.1
- NIST CSF 2.0: PR.PS-01
- CWE: CWE-862
- NIST SP 800-53 Rev. 5: AC-6, CM-7
- Benchmark topic: Restrict cron and at to authorised users (CIS Controls v8 4.1) (topic only, no benchmark text)

## Why It Matters

By default every local account may schedule jobs. A deny list only names known accounts; an allow list says exactly who may schedule, which is what least privilege asks for and what makes persistence by a compromised service account harder.

## How It Detects

Stats /etc/cron.allow and /etc/at.allow (metadata only). For each scheduler that is installed (/etc/crontab or /etc/cron.d for cron, /etc/at.deny, /etc/at.allow or /var/spool/at for at), a missing allow file, an allow file not owned by root, or one readable or writable by group or others fails. A deny file present without an allow file is reported.

## How to Fix

Create the allow lists:  touch /etc/cron.allow /etc/at.allow && chmod 600 /etc/cron.allow /etc/at.allow && chown root:root /etc/cron.allow /etc/at.allow  then add one user name per line for the accounts that need scheduling, and remove /etc/cron.deny and /etc/at.deny. Caution: once cron.allow exists, crontabs of users not listed stop running, so list every service and user account that has a crontab (ls /var/spool/cron/crontabs or /var/spool/cron) before creating it.

## How to Verify

```
stat -c '%a %U %n' /etc/cron.allow /etc/at.allow; ls /etc/cron.deny /etc/at.deny 2>&1
```

## 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

- [crontab(1), Linux man-pages (cron.allow and cron.deny)](https://man7.org/linux/man-pages/man1/crontab.1.html)
- [at(1), Linux man-pages (at.allow and at.deny)](https://man7.org/linux/man-pages/man1/at.1.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-019`. Read it offline: `openvapt explain HOST-FS-019`.

---

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