openSUSE Tumbleweed — fail2ban — multiple vulnerabilities (5 CVEs) — patch and remediation guide

📖 ~4 min read  •  Source: SUSE security advisory (see also SUSE bugzilla)

Related CVEs: CVE-2009-5023 CVE-2013-2178 CVE-2013-7176 CVE-2013-7177 CVE-2021-32749

Upstream summary: The (1) dshield.conf, (2) mail-buffered.conf, (3) mynetwatchman.conf, and (4) mynetwatchman.conf actions in action.d/ in Fail2ban before 0.8.5 allows local users to write to arbitrary files via a symlink attack on temporary files with predictable names, as demonstrated by /tmp/fail2ban-mail.txt.

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

fail2ban runs as a long-lived process on openSUSE Tumbleweed, started at boot and holding open sockets (visible in ss -lntp), so a flaw in it stays reachable for as long as the service is up. Exploitation usually means code execution in the daemon’s own security context, memory disclosure from a process holding credentials and cached client data, or a crash that takes the listener down. Workers started before the upgrade keep running the old binary until the unit is reloaded or restarted. fail2ban is a genuine long-running service, so restart steps do apply — but confirm the unit name first with systemctl list-unit-files | grep -i fail2ban, since it often differs from the package name (bind ships named.service).

Environment & Reproduction

Reproduction targets openSUSE Tumbleweed. Confirm release and installed package:

cat /etc/os-release
rpm -q fail2ban
zypper info fail2ban | head -20
zypper lr -E                              # enabled repositories

Exercise the workload that uses fail2ban while collecting:

sudo journalctl -u fail2ban -b --no-pager | tail -200
sudo journalctl -xe --no-pager | tail -200
sudo tail -200 /var/log/zypp/history
sudo journalctl -k | grep -i apparmor | tail -100
# Bundle evidence for SUSE / community support:
sudo supportconfig -R /var/tmp -B fail2ban

Root Cause Analysis

Root cause is documented in SUSE security advisory. openSUSE security maintainers shipped fixes in the corresponding fail2ban update for openSUSE Tumbleweed; running an outdated build leaves the host exposed to the failure modes described in the advisory. Correlate zypper history with system logs:

sudo zypper history | grep fail2ban
sudo zypper history --since='-7 days' | tail -40
sudo journalctl -k | grep -i apparmor | tail -100
cat /proc/sys/kernel/tainted   # non-zero = tainted kernel / out-of-tree modules
snapper list | tail -20         # snapshots taken around each zypper transaction

Quick Triage

Run these on openSUSE Tumbleweed to capture the current state of fail2ban:

rpm -q fail2ban                              # installed NVR
rpm -V fail2ban                              # verify shipped files
sudo zypper ref                            # refresh repos
sudo zypper dup --dry-run                  # pending rolling updates
systemctl --failed --no-pager
sudo firewall-cmd --list-all
sudo aa-status                             # AppArmor profiles
# fail2ban runs as the "fail2ban" service - restart it once the upgrade is in place:
# bind→named, postgresql-server→postgresql, php-fpm→php-fpm):
systemctl list-unit-files | grep -i fail2ban | head

Step-by-Step Diagnosis

1. List failed systemd units.

   systemctl --failed --no-pager

2. Tail the journal for fail2ban and the system bus.

   sudo journalctl -u fail2ban -f --no-pager
   sudo journalctl -xe -f --no-pager

3. Inspect firewall posture (firewalld is the default on openSUSE).

   sudo firewall-cmd --list-all-zones --permanent
   sudo nft list ruleset 2>/dev/null | head -50

4. Surface AppArmor denials and switch the profile to complain mode if needed.

   sudo journalctl -k | grep -i 'apparmor="DENIED"' | tail -30
   sudo aa-status
   sudo aa-complain /etc/apparmor.d/usr.sbin.fail2ban 2>/dev/null || true

5. Verify fail2ban integrity and reinstall if anything is altered.

   sudo rpm -V fail2ban
   sudo zypper verify
   sudo zypper install --force fail2ban

6. Inspect Snapper snapshots to know exactly which transaction introduced the regression.

   sudo snapper list | tail -20
   sudo snapper status <pre-id>..<post-id>

7. Correlate findings with /var/log/zypp/history, zypper history, and SUSE security advisory to pin the change that introduced the regression.

Solution – Primary Fix

Apply the corrective zypper transaction referenced by SUSE security advisory, then reload affected systemd units:

sudo zypper ref                                      # refresh repos
# Tumbleweed is a rolling release — use 'dup', not 'patch':
sudo zypper dup --no-allow-vendor-change             # rolling distribution upgrade
# To target only the affected package while still on rolling:
sudo zypper dup --no-allow-vendor-change fail2ban
sudo systemctl daemon-reload
# Unit name may differ from pkg name; check first:
systemctl list-unit-files | grep -i fail2ban | head
sudo systemctl restart fail2ban
rpm -q fail2ban                                          # confirm new NVR
systemctl is-active fail2ban 2>/dev/null                 # confirm running (if a unit exists)

For kernel / glibc / systemd / openssl rolls a reboot is required. Tumbleweed does not ship Live Patching, so plan a maintenance window or use Snapper to roll back if a regression appears:

sudo zypper ps -s                      # services using deleted libs
sudo snapper list | tail -5            # confirm pre/post snapshots exist
sudo systemctl reboot                  # or: sudo shutdown -r now

Solution – Alternative Approaches

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

• Roll back via Snapper (Btrfs snapshots are taken automatically before zypper transactions on openSUSE Tumbleweed). This is the primary safety net for openSUSE administrators:

  sudo snapper list
  sudo snapper status <pre-id>..<post-id>   # diff between two snapshot numbers
  sudo snapper undochange <pre-id>..<post-id>
  sudo snapper rollback <pre-id>            # boot the host into the chosen snapshot
  sudo systemctl reboot

• Lock the package so zypper cannot upgrade it:

  sudo zypper al fail2ban                   # add lock
  zypper ll | grep fail2ban                 # list locks
  sudo zypper rl fail2ban                   # remove lock

• Install an older NVR if a regression is suspected:

  zypper se -s fail2ban                     # show all available versions
  sudo zypper install --oldpackage fail2ban-<older-NVR>

• Disable the AppArmor profile briefly to confirm policy is the cause, then re-enable:

  sudo aa-disable /etc/apparmor.d/usr.sbin.fail2ban
  # reproduce, capture denials in the journal:
  sudo journalctl -k | grep apparmor | tail
  sudo aa-enforce /etc/apparmor.d/usr.sbin.fail2ban

• Pin Tumbleweed to a known-good snapshot from the openSUSE history server while you investigate. This keeps the rolling release reproducible across a fleet:

  # Edit /etc/zypp/repos.d/repo-oss.repo and point baseurl at
  #   http://download.opensuse.org/history/<YYYYMMDD>/tumbleweed/repo/oss/
  sudo zypper ref
  sudo zypper dup --no-allow-vendor-change

Verification & Acceptance Criteria

All of these should pass after the fix:

rpm -q fail2ban                                            # expected fixed NVR
sudo zypper dup --dry-run                                # no pending rolls expected
systemctl is-active fail2ban 2>/dev/null
sudo journalctl -u fail2ban --since "5 minutes ago" --no-pager | grep -iE "error|fail" || echo OK
sudo firewall-cmd --list-services
sudo aa-status | head -5
sudo zypper ps -s                                        # any services still using deleted libs

The conditions described in the advisory must no longer be reported for fail2ban across two consecutive runs.

Rollback Plan

Capture state before any change. On openSUSE, Snapper is the canonical rollback path:

rpm -qa > /root/rpm-pre.txt
sudo zypper history list > /root/zypper-history-pre.txt
# Snapper takes pre/post snapshots automatically on Btrfs root.
sudo snapper create -d 'pre-patch-fail2ban'   # explicit named snapshot
sudo snapper list | head

To revert if the patch / roll is bad:

# Preferred on Btrfs root — boot the prior snapshot:
sudo snapper list
sudo snapper rollback <pre-id>
sudo systemctl reboot
# Or downgrade just the package:
sudo zypper install --oldpackage fail2ban-<older-NVR>
sudo systemctl daemon-reload
sudo systemctl restart fail2ban
# Custom AppArmor profile cleanup:
sudo apparmor_parser -R /etc/apparmor.d/usr.sbin.fail2ban

Prevention & Hardening

Reduce the chance of this recurring on openSUSE Tumbleweed:

• Run rolling upgrades on a schedule — Tumbleweed receives a snapshot most weekdays. Stagger across the fleet so any regression is caught early:

  sudo zypper ref
  sudo zypper dup --no-allow-vendor-change
  # Optional: drive from salt/ansible with a maintenance window per host group.

• Subscribe to opensuse-security-announce and watch suse.com/support/update.

• Lock sensitive packages so they cannot be auto-upgraded:

  sudo zypper al fail2ban

• Ensure Snapper is enabled on the root subvolume and pre/post hooks run for every zypper transaction. This is the cornerstone of safe openSUSE patching:

  sudo snapper -c root get-config | head
  # Default zypper plugin: /usr/lib/zypp/plugins/commit/snapper.zypp-commit-plugin
  sudo snapper list | tail -10

• Monitor file integrity with AIDE:

  sudo zypper install -y aide
  sudo aide --init && sudo mv /var/lib/aide/aide.db.new /var/lib/aide/aide.db
  sudo aide --check

• Keep AppArmor profiles in enforce; review /etc/apparmor.d/ after every package upgrade.

• Apply CIS / openSUSE hardening guidance and use salt or ansible to enforce baseline state across the fleet.

Related Errors & Cross-Refs

Issues that commonly surface alongside a fail2ban update: zypper lock contention, systemd unit ordering cycles, AppArmor denials, firewalld zone drift, and kernel taint flags. Useful triage:

sudo zypper ps -s
systemd-analyze critical-chain
sudo journalctl -k | grep apparmor | tail
sudo firewall-cmd --get-active-zones
cat /proc/sys/kernel/tainted
sudo snapper list | tail

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References & Further Reading

Primary reference: SUSE security advisory (see also SUSE bugzilla). Manual pages useful on openSUSE Tumbleweed:

man zypper
man zypper.conf
man systemctl
man journalctl
man firewall-cmd
man snapper
man apparmor
man aa-status

Other resources: openSUSE documentation, suse.com/security, openSUSE security portal, and per-package notes in /usr/share/doc/packages/fail2ban/ for components implicated in this advisory.

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