FreeBSD 13 — nomad — vulnerability — patch and remediation guide

📖 ~4 min read  •  Source: FreeBSD VuXML

VuXML topic: nomad — multiple vulnerabilities

Related CVEs: CVE-2020-27195

Upstream summary: The HashiCorp team reports: artifact: Fixed a bug where interpolation can be used in the artifact destination field to write artifact payloads outside the allocation directory. template: Fixed a bug where interpolation can be used in the template source and destination fields to read or write files outside the allocation directory even when disable_file_sandbox was set to false (the default). template: Fixed a bug where the disable_file_sandbox configuration was only respecte

Table of contents

1. Symptom & Impact
2. Environment & Reproduction
3. Root Cause Analysis
4. Quick Triage
5. Step-by-Step Diagnosis
6. Solution – Primary Fix
7. Solution – Alternative Approaches
8. Verification & Acceptance Criteria
9. Rollback Plan
10. Prevention & Hardening
11. Related Errors & Cross-Refs
12. References & Further Reading

Symptom & Impact

nomad runs when an image is pulled, unpacked, inspected or a container is started, so a defect here is normally reached through untrusted image content or a registry response rather than inbound traffic to a listening port. On FreeBSD 13 that shows up as escapes from the container’s namespaces, files written outside the intended root during buildah or podman build, mount and capability handling that grants more than was requested, and images produced before the update carrying the defect onward to every host that pulls them. nomad is container tooling — command-line binaries invoked per operation, though a node runtime such as cri-o does run as a unit — so restart steps apply to that runtime and to containers still running the old code, not to nomad itself.

Environment & Reproduction

Reproduction targets FreeBSD 13. Confirm release, installed package, and capture baseline state:

freebsd-version -kru
uname -a
pkg info nomad
pkg query "%n-%v" nomad
pkg audit -F
service -e

Exercise the workload that uses nomad while collecting:

tail -200 /var/log/messages
dmesg -a | tail -200
tail -200 /var/log/pkg.log

Root Cause Analysis

Root cause is tracked at FreeBSD VuXML. The FreeBSD ports security team shipped a corrective nomad port revision; hosts on an outdated build remain exposed. Correlate package logs with system logs and kernel state to isolate the change that triggered the failure mode:

tail -500 /var/log/pkg.log
tail -500 /var/log/messages
sysctl kern.lastpid
sysctl kern.osreldate     # numeric __FreeBSD_version, e.g. 1400097

Quick Triage

Run these checks on FreeBSD 13 to confirm the failure mode and current state of nomad:

pkg version -v nomad                # installed vs available version
pkg audit nomad                     # advisory match for this package
tail -100 /var/log/messages
dmesg -a | tail -100
kldstat                              # kernel module state (for kernel/driver pkgs)
pfctl -sr 2>/dev/null || ipfw list   # only if pf/ipfw is enabled
# nomad runs as the "nomad" service - restart it once the upgrade is in place:
# e.g. bind918→named, php83→php-fpm), check it:
service -e | grep -i nomad && service nomad status

Step-by-Step Diagnosis

1. List enabled services (only relevant if the package provides one).

   service -e

2. Follow live logs.

   tail -F /var/log/messages
   dmesg

3. Validate firewall rules (skip if neither pf nor ipfw is enabled).

   pfctl -sr -v 2>/dev/null || ipfw show

4. Check package integrity for nomad.

   pkg check -B nomad
   pkg check -d nomad    # verify shared-library deps

5. Reinstall nomad if integrity check fails.

   pkg install -fy nomad

6. Correlate findings with /var/log/pkg.log and FreeBSD VuXML to pin the commit that introduced the regression.

Solution – Primary Fix

Install the corrective nomad port revision referenced by FreeBSD VuXML:

sudo pkg update
sudo pkg upgrade nomad              # or: sudo pkg upgrade -y for the whole system
# nomad runs as the "nomad" service - restart it once the upgrade is in place:
sudo service nomad restart
pkg audit nomad                    # confirm no remaining advisory for this package

For ports-tree builders (FreeBSD 13.x and earlier used portsnap; on FreeBSD 14+ the ports tree is fetched with Git):

# FreeBSD 14+ (portsnap was removed):
sudo pkg install -y git-lite
sudo git clone --depth 1 https://git.FreeBSD.org/ports.git /usr/ports
# FreeBSD 13.x and earlier:
# sudo portsnap fetch update
cd /usr/ports/<category>/nomad
sudo make deinstall reinstall clean

Reboot only if the package ships a kernel module or replaces a shared library used by long-running daemons.

Solution – Alternative Approaches

If the primary fix is not viable, choose from these alternatives:

• Lock the package until the fix is vetted:

  sudo pkg lock nomad

• Downgrade to a known-good revision. pkg install pkgname-VERSION is not a real downgrade syntax — fetch a specific build instead:

  # 1. Discover available versions across configured repos:
  pkg search -e nomad
  pkg rquery -r FreeBSD-quarterly '%n-%v' nomad
  # 2. Install from a specific saved .pkg file:
  sudo pkg add -f /path/to/nomad-<older-version>.pkg
  # 3. Or switch the host repo to the quarterly branch (see snippet below) and:
  sudo pkg upgrade -fr FreeBSD-quarterly nomad

• Switch the pkg repository between quarterly and latest by editing /usr/local/etc/pkg/repos/FreeBSD.conf:

  FreeBSD: {
    url: "pkg+https://pkg.FreeBSD.org/${ABI}/quarterly",
    mirror_type: "srv",
    signature_type: "fingerprints",
    fingerprints: "/usr/share/keys/pkg",
    enabled: yes
  }

• Isolate the affected service in a jail with stricter firewall rules:

  iocage create -n nomad-jail -r 13.4-RELEASE
  iocage set allow_raw_sockets=0 nomad-jail
  # or with Bastille:
  bastille create nomad-jail 13.4-RELEASE 10.0.0.10

• Replace the service with a vendored static build for the period between exposure detection and full rollout.

Verification & Acceptance Criteria

All of these should pass after the fix:

pkg info nomad                # shows the expected fixed version
pkg audit nomad               # no advisory for this package (exit code 0)
tail -50 /var/log/messages   # no new errors after upgrade
# If nomad ships a service, confirm it is running under its rc.d name:
# service nomad status

The conditions described in the advisory must no longer be reported for nomad across two consecutive runs.

Rollback Plan

Capture state before any change (only ZFS root has boot environments — UFS hosts skip bectl):

pkg query "%n-%v" > /root/pkg-pre.txt
# ZFS-on-root only:
sudo bectl create pre-nomad-patch

To revert if the upgrade is bad, reinstall the previously saved .pkg file:

sudo pkg add -f /var/cache/pkg/nomad-<previous-version>.pkg
# Or activate the pre-patch boot environment and reboot (ZFS-on-root only):
sudo bectl activate pre-nomad-patch
sudo shutdown -r now

For kernel/loader changes on a UFS host, boot the previous kernel from the loader prompt (press 3 at the menu, then boot kernel.old).

Prevention & Hardening

Prevent recurrence on FreeBSD 13 hosts running nomad:

• Enable the daily security pkg audit in /etc/periodic.conf:

  daily_status_security_pkgaudit_enable="YES"

• Subscribe to freebsd-security-notifications at lists.freebsd.org.

• Mirror through a local pkg repository managed by poudriere:

  poudriere jail -c -j 13amd64 -v 13.4-RELEASE
  poudriere ports -c -p default
  poudriere bulk -j 13amd64 -p default <category>/nomad

• Version-pin sensitive packages:

  sudo pkg lock nomad

• Take an automatic ZFS boot-environment snapshot before every upgrade (ZFS root only):

  sudo bectl create pre-upgrade-$(date +%Y%m%d)

• Monitor file integrity (create a baseline, verify against it later):

  # Create a baseline (use -c; target /usr/local/etc, /etc, /boot — NOT /):
  sudo mtree -c -K sha256digest -p /usr/local/etc > /var/db/usr-local-etc.mtree
  sudo mtree -c -K sha256digest -p /etc          > /var/db/etc.mtree
  # Verify later:
  sudo mtree -p /usr/local/etc < /var/db/usr-local-etc.mtree
  # Or with AIDE for a richer ruleset:
  sudo pkg install -y aide && sudo aide --init && sudo aide --check

• Harden jails with allow.* tunables in /etc/jail.conf:

  nomad_jail {
    allow.raw_sockets = 0;
    allow.sysvipc    = 0;
    allow.mount      = 0;
    allow.chflags    = 0;
  }

Related Errors & Cross-Refs

Issues that commonly surface alongside a nomad update: pkg lock contention, mismatched ABI after kernel/userland skew, pf rule drift, and stale shared-library references after upgrade. Triage with:

freebsd-version -kru
uname -K
pkg check -d
pfctl -sr

View all freebsd-13 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

Primary reference: FreeBSD VuXML. Useful manual pages on FreeBSD 13:

man pkg
man freebsd-update
man pfctl
man ipfw
man bectl
man periodic.conf

Other resources: the FreeBSD Handbook, the FreeBSD Security Advisories at security.freebsd.org, and the /usr/ports/UPDATING file for port-specific notes implicated in this advisory.