SLES 15 — libzmq5 — multiple vulnerabilities (6 CVEs) — patch and remediation guide

📖 ~4 min read  •  Source: SUSE advisory SUSE-FU-2022:0444-1 (see also SUSE bugzilla)

Related CVEs: CVE-2019-13132 CVE-2019-6250 CVE-2020-15166 CVE-2014-7202 CVE-2014-7203 CVE-2014-9721

Upstream summary: In ZeroMQ libzmq before 4.0.9, 4.1.x before 4.1.7, and 4.2.x before 4.3.2, a remote, unauthenticated client connecting to a libzmq application, running with a socket listening with CURVE encryption/authentication enabled, may cause a stack overflow and overwrite the stack with arbitrary data, due to a buffer overflow in the library. Users running public servers with the above configuration are highly encouraged to upgrade as soon as possible, as there are no known mitigations

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

On SLES 15 hosts that have libzmq5 installed, administrators report behaviour consistent with SUSE advisory SUSE-FU-2022:0444-1: zypper patch-check lists open patches, services backed by libzmq5 fail or restart unexpectedly, AppArmor profile warnings appear in journalctl -k — and for security-rated advisories the host is exposed to the vulnerability set above. Impact ranges from a single service-restart loop to wider availability incidents whenever libzmq5 sits on the serving path.

Environment & Reproduction

Reproduction targets SLES 15. Confirm release, registration, and installed package:

cat /etc/os-release
SUSEConnect --status-text
SUSEConnect --list-extensions 2>/dev/null | head -30
rpm -q libzmq5
zypper info libzmq5 | head -20

Trigger the workflow that exposes libzmq5 — multiple vulnerabilities (6 CVEs) — patch and remediation guide while collecting:

sudo journalctl -u libzmq5 -b --no-pager | tail -200
sudo journalctl -xe --no-pager | tail -200
sudo tail -200 /var/log/zypp/history
sudo tail -200 /var/log/audit/audit.log
# For SUSE support, bundle evidence with supportconfig:
sudo supportconfig -R /var/tmp -B libzmq5

Root Cause Analysis

Root cause is documented in SUSE advisory SUSE-FU-2022:0444-1. SUSE security maintainers shipped fixes in the corresponding libzmq5 update for SLES 15; running an outdated build leaves the host exposed to the failure modes described in the advisory.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 libzmq5
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

Quick Triage

Run these on SLES 15 to capture the current state of libzmq5:

rpm -q libzmq5                              # installed NVR
rpm -V libzmq5                              # verify shipped files
sudo zypper patch-check                    # open patches
sudo zypper lp -r SUSE-SLE-Server-15-* 2>/dev/null | head
systemctl --failed --no-pager
sudo firewall-cmd --list-all
sudo aa-status                              # AppArmor profiles
# If libzmq5 ships a systemd unit (unit name may differ from pkg name, e.g.
# bind→named, postgresql-server→postgresql, php-fpm→php-fpm):
systemctl list-unit-files | grep -i libzmq5 | head

Step-by-Step Diagnosis

1. List failed systemd units.

   systemctl --failed --no-pager

2. Tail the journal for libzmq5 and the system bus.

   sudo journalctl -u libzmq5 -f --no-pager
   sudo journalctl -xe -f --no-pager

3. Inspect firewall posture (firewalld is the default on SLES 15+).

   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.libzmq5 2>/dev/null || true

5. Verify libzmq5 integrity and reinstall if anything is altered.

   sudo rpm -V libzmq5
   sudo zypper verify
   sudo zypper install --force libzmq5

6. Correlate findings with /var/log/zypp/history, zypper history, and SUSE advisory SUSE-FU-2022:0444-1 to pin the change that introduced libzmq5 — multiple vulnerabilities (6 CVEs) — patch and remediation guide.

Solution – Primary Fix

Apply the corrective zypper transaction referenced by SUSE advisory SUSE-FU-2022:0444-1, then reload affected systemd units:

sudo zypper ref                        # refresh repos
sudo zypper -n patch                   # apply ALL open patches (recommended)
# Or target a single package:
sudo zypper -n update libzmq5
sudo systemctl daemon-reload
# Unit name may differ from pkg name; check first:
systemctl list-unit-files | grep -i libzmq5 | head
sudo systemctl restart libzmq5
rpm -q libzmq5                           # confirm new NVR
systemctl is-active libzmq5 2>/dev/null  # confirm running (if a unit exists)

For kernel / glibc / systemd / openssl advisories a reboot is required (or SLE Live Patching where licensed):

sudo zypper ps -s                      # services using deleted libs
sudo systemctl reboot                  # or: sudo shutdown -r now
# SUSE Live Patching (kgraft / klp) avoids reboot for kernel CVEs:
sudo zypper install -y kernel-livepatch-$(uname -r | tr - _)
klp -v patches                         # active livepatches

Solution – Alternative Approaches

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

• Roll back via Snapper (Btrfs snapshots taken automatically before zypper transactions on SLES 15):

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

• Lock the package so zypper cannot upgrade it:

  sudo zypper al libzmq5                   # add lock
  zypper ll | grep libzmq5                 # list locks
  sudo zypper rl libzmq5                   # remove lock

• Install an older NVR if a regression is suspected:

  zypper se -s libzmq5                     # show all available versions
  sudo zypper install --oldpackage libzmq5-<older-NVR>

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

  sudo aa-disable /etc/apparmor.d/usr.sbin.libzmq5
  # reproduce, capture denials in the journal:
  sudo journalctl -k | grep apparmor | tail
  sudo aa-enforce /etc/apparmor.d/usr.sbin.libzmq5

• Where SLE Live Patching is licensed, apply kernel fixes without reboot:

  klp -v patches                         # active livepatches
  sudo zypper install -y kernel-livepatch-$(uname -r | tr - _)

Verification & Acceptance Criteria

All of these should pass after the fix:

rpm -q libzmq5                                            # expected fixed NVR
sudo zypper patch-check                                  # 0 critical patches outstanding
systemctl is-active libzmq5 2>/dev/null
sudo journalctl -u libzmq5 --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 original reproduction for libzmq5 — multiple vulnerabilities (6 CVEs) — patch and remediation guide must not trigger across two consecutive runs.

Rollback Plan

Capture state before any change:

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-libzmq5'   # explicit named snapshot
sudo snapper list | head

To revert if the patch is bad:

# Preferred on Btrfs root — boot the prior snapshot:
sudo snapper rollback <snapshot-id>
sudo systemctl reboot
# Or downgrade just the package:
sudo zypper install --oldpackage libzmq5-<older-NVR>
sudo systemctl daemon-reload
sudo systemctl restart libzmq5
# Custom security policy cleanup:
sudo apparmor_parser -R /etc/apparmor.d/usr.sbin.libzmq5

Prevention & Hardening

Reduce the chance of this recurring on SLES 15:

• Enable automatic patch installation:

  sudo zypper install -y zypper-automatic
  sudo systemctl enable --now zypper-automatic.timer
  # Or use YaST: yast2 online_update_configuration

• Subscribe to sle-security-updates and watch suse.com/support/update.

• Mirror through SUSE Manager or RMT (Repository Mirroring Tool) for controlled rollouts:

  sudo zypper install -y rmt-server rmt-cli
  sudo rmt-cli sync
  sudo rmt-cli products enable SLES/15/x86_64

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

  sudo zypper al libzmq5

• Ensure Snapper is enabled on the root subvolume and pre/post hooks run for every zypper transaction:

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

• 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

• Subscribe to SUSE Live Patching so kernel CVEs can be remediated without reboot:

  sudo SUSEConnect -p sle-module-live-patching/15.0/x86_64
  sudo zypper install -y kernel-livepatch-$(uname -r | tr - _)
  klp -v patches

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

• Apply CIS SUSE Linux Enterprise Server Benchmark hardening.

Related Errors & Cross-Refs

Issues that commonly surface alongside libzmq5 — multiple vulnerabilities (6 CVEs) — patch and remediation guide: 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

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References & Further Reading

Primary reference: SUSE advisory SUSE-FU-2022:0444-1 (see also SUSE bugzilla). Manual pages useful on SLES 15:

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

Other resources: SUSE Linux Enterprise Server 15 documentation, suse.com/security, SUSE security blog, and per-package notes in /usr/share/doc/packages/libzmq5/ for components implicated in libzmq5 — multiple vulnerabilities (6 CVEs) — patch and remediation guide.