Debian 12 — firehol — multiple vulnerabilities (2 CVEs) — patch and remediation guide

📖 ~4 min read  •  Source: Debian Security Tracker

Related CVEs: CVE-2005-0225 CVE-2008-4953

Upstream summary: firehol.sh in FireHOL before 1.224 creates temporary files with predictable file names, which could allow local users to overwrite arbitrary files via a symlink attack.

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

Nothing visibly changes on a Debian 12 host until firehol is next invoked: it runs, exits and leaves no daemon behind, so there is no restart loop or service log to watch. Exposure is per-invocation, and the invocations that matter are the unattended ones — cron jobs, backup and deployment scripts, CI runners, and anything passing attacker-influenced input such as a remote URL, a supplied archive or an untrusted filename. Where firehol is run under sudo or from a privileged job, the same flaw becomes local privilege escalation. firehol ships command-line programs that run when invoked and then exit, so there is no unit to restart — systemctl and journalctl -u have nothing to act on; only the next invocation matters.

Environment & Reproduction

Reproduction targets Debian 12 (bookworm). Confirm release and installed package:

cat /etc/debian_version
lsb_release -a 2>/dev/null || cat /etc/os-release
dpkg -l firehol | tail -2
apt-cache policy firehol
dpkg-query -W -f='${Status}\n' firehol

Exercise the workload that uses firehol while collecting:

sudo journalctl -xe --no-pager | tail -200
sudo tail -200 /var/log/apt/history.log
sudo tail -200 /var/log/dpkg.log

Root Cause Analysis

Root cause is tracked at Debian Security Tracker. The Debian Security Team shipped fixes in the corresponding firehol point release for Debian 12 (suite bookworm-security); running an outdated build leaves the host exposed to the failure modes referenced above. Correlate apt history with the journal:

grep -A2 -B2 firehol /var/log/apt/history.log
zgrep -A2 -B2 firehol /var/log/apt/history.log.*.gz 2>/dev/null
cat /proc/sys/kernel/tainted   # non-zero = tainted kernel / out-of-tree modules

Quick Triage

Run these on Debian 12 to capture the current state of firehol:

dpkg -l firehol | tail -1                   # installed version
dpkg -V firehol                              # verify shipped files
sudo apt update && apt list --upgradable 2>/dev/null | grep -i security
systemctl --failed --no-pager
sudo nft list ruleset 2>/dev/null | head -50
sudo aa-status 2>/dev/null | head -20      # AppArmor profiles
dpkg-query -L firehol 2>/dev/null | grep -E '^/etc/init\.d/[^/]+$'  # legacy SysV init script; its basename is the service name for 'service <name> restart' on non-systemd hosts
systemctl list-unit-files --no-pager --type=service,socket,timer | grep -iF -- 'firehol'  # fuzzy name match; -F is required because package names contain regex metacharacters ('+' in libstdc++6/g++-13 makes -E fail to match at all)

Step-by-Step Diagnosis

1. List failed systemd units.

   systemctl --failed --no-pager

2. Tail the journal for firehol and the system bus.

   sudo journalctl -xe -f --no-pager

3. Inspect firewall state (this OS defaults to nftables).

   sudo nft list ruleset
   sudo nft list tables

4. Verify firehol file integrity and reinstall if anything is altered.

   sudo dpkg -V firehol
   sudo debsums -c firehol 2>/dev/null
   sudo apt install --reinstall -y firehol

5. Check AppArmor denials (Debian 11+ default-enabled).

   sudo journalctl -k | grep -i 'apparmor="DENIED"' | tail -30
   sudo aa-status | grep -i firehol

6. Correlate findings with /var/log/apt/history.log, /var/log/dpkg.log, and Debian Security Tracker to pin the change that introduced the regression.

Solution – Primary Fix

Apply the corrective apt transaction documented in Debian Security Tracker from the security suite, then reload the affected unit:

sudo apt update
sudo apt -y install --only-upgrade firehol
# Unit name may differ from package name; check first:
dpkg -l firehol | tail -1                # confirm new version

For kernel / glibc / systemd / openssl advisories a reboot is required:

sudo apt install -y needrestart
sudo needrestart -r l       # list services that need restart
sudo systemctl reboot       # or: sudo shutdown -r now

Solution – Alternative Approaches

If the primary upgrade is not viable, pick from these:

• Pin a known-good version via apt preferences:

  # /etc/apt/preferences.d/firehol.pref
  Package: firehol
  Pin: version <good-version>
  Pin-Priority: 1001

• Mark the package on hold so apt cannot upgrade it:

  sudo apt-mark hold firehol
  apt-mark showhold | grep firehol
  # Release the hold later with:
  sudo apt-mark unhold firehol

• Downgrade to an older NVR if a regression is suspected:

  apt-cache madison firehol
  sudo apt install --allow-downgrades -y firehol=<older-version>

• Switch firewall backend between iptables-legacy and nftables (Debian 10+):

  sudo update-alternatives --config iptables
  sudo update-alternatives --config ip6tables
  sudo systemctl restart netfilter-persistent 2>/dev/null

• Take only the security archive update and defer the full point-release upgrade:

  # /etc/apt/sources.list.d/bookworm-security-only.list
  deb http://security.debian.org/debian-security bookworm-security main contrib non-free
  # then:
  sudo apt update && sudo apt -y install --only-upgrade -t bookworm-security firehol

• Investigate AppArmor blocking the new binary; switch the profile to complain mode briefly:

  # reproduce, capture denials, then re-enforce:

Verification & Acceptance Criteria

All of these should pass after the fix is applied:

dpkg -l firehol | tail -1                                  # expected fixed version
apt list --upgradable 2>/dev/null | grep -i security || echo OK
sudo nft list ruleset | head
sudo aa-status 2>/dev/null | head -5

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

Rollback Plan

Capture state before any change:

apt list --installed 2>/dev/null > /root/apt-pre.txt
dpkg --get-selections > /root/dpkg-pre.txt
# LVM snapshot of the root LV (only if root sits on LVM):
sudo lvcreate -L 4G -s -n root_pre_patch /dev/<vg>/<root-lv>

To revert:

sudo apt install --allow-downgrades -y firehol=<old-version>
# If a kernel was rolled back, reboot and select the previous kernel from GRUB:
sudo systemctl reboot
# LVM snapshot merge (offline / on next reboot):
sudo lvconvert --merge /dev/<vg>/root_pre_patch

Prevention & Hardening

Reduce the chance of this recurring on Debian 12:

• Enable scheduled security updates via unattended-upgrades:

  sudo apt install -y unattended-upgrades apt-listchanges
  sudo dpkg-reconfigure -plow unattended-upgrades
  # /etc/apt/apt.conf.d/50unattended-upgrades:
  Unattended-Upgrade::Origins-Pattern { "origin=Debian,codename=${distro_codename},label=Debian-Security"; };

• Install needrestart so services restart automatically after library upgrades:

  sudo apt install -y needrestart
  # /etc/needrestart/needrestart.conf -> $nrconf{restart} = 'a';

• Subscribe to debian-security-announce and watch security-tracker.debian.org.

• Mirror locally for controlled rollouts:

  sudo apt install -y apt-mirror
  # /etc/apt/mirror.list:
  deb http://deb.debian.org/debian bookworm main contrib non-free
  deb http://security.debian.org/debian-security bookworm-security main contrib non-free
  sudo apt-mirror

• Monitor file integrity with debsums and AIDE:

  sudo apt install -y debsums aide
  sudo debsums -ca           # report only changed conffile-less files
  sudo aideinit && sudo mv /var/lib/aide/aide.db.new /var/lib/aide/aide.db
  sudo aide --check

• Apply CIS Debian Linux Benchmark hardening and review auditd rules in /etc/audit/rules.d/.

Related Errors & Cross-Refs

Issues that commonly surface alongside a firehol update: apt lock contention, broken dpkg state, systemd ordering cycles, AppArmor denials, and firewall rule drift. Useful triage:

sudo dpkg --configure -a
sudo apt --fix-broken install
systemd-analyze critical-chain
sudo journalctl -k | grep -i apparmor | tail
cat /proc/sys/kernel/tainted

View all debian-12 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

Primary reference: Debian Security Tracker. Manual pages useful on Debian 12:

man apt
man apt-get
man apt-mark
man dpkg
man systemctl
man journalctl
man nft
man apparmor
man unattended-upgrades

Other resources: The Debian Administrator’s Handbook, Debian Security FAQ, Debian Security Tracker, and per-package notes in /usr/share/doc/firehol/ for components implicated in this advisory.