Ubuntu 18.04 — docker-registry — multiple vulnerabilities (2 CVEs) — patch and remediation guide

📖 ~4 min read  •  Source: Ubuntu Security Notice USN-6336-1

Related CVEs: CVE-2017-11468 CVE-2023-2253

Upstream summary: It was discovered that Docker Registry incorrectly handled certain crafted
input, A remote attacker could possibly use this issue to cause a denial
of service. This issue only affected Ubuntu 16.04 LTS. (CVE-2017-11468)

It was discovered that Docker Registry incorrectly handled certain crafted
input. An attacker could possibly use this issue to cause a denial of
service. (CVE-2023-2253)

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

docker-registry 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 Ubuntu 18.04 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. docker-registry 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 docker-registry itself.

Environment & Reproduction

Reproduction targets Ubuntu 18.04 (bionic). Confirm release and installed package:

lsb_release -a
cat /etc/os-release
dpkg -l docker-registry | tail -2
apt-cache policy docker-registry
uname -r

Exercise the workload that uses docker-registry while collecting:

sudo journalctl -u docker-registry -b --no-pager | tail -200
sudo journalctl -xe --no-pager | tail -200
sudo tail -200 /var/log/apt/history.log
sudo tail -200 /var/log/kern.log | grep -i apparmor

Root Cause Analysis

Root cause is documented in Ubuntu Security Notice USN-6336-1. Canonical security maintainers shipped fixes in the corresponding docker-registry update for Ubuntu 18.04; running an outdated build leaves the host exposed to the failure modes described in the advisory. On this release the fix typically arrives via the Ubuntu Pro ESM (esm-infra / esm-apps) channels rather than the standard archive. Correlate apt history with the journal:

grep -A2 -B2 docker-registry /var/log/apt/history.log
zgrep -A2 -B2 docker-registry /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 Ubuntu 18.04 to capture the current state of docker-registry:

dpkg -l docker-registry | tail -1                  # installed version
dpkg -V docker-registry                             # verify shipped files
sudo apt update && apt list --upgradable 2>/dev/null | grep -i security
systemctl is-active docker-registry
sudo ufw status verbose 2>/dev/null | head -20
sudo aa-status 2>/dev/null | head -20
# If docker-registry ships a service unit (unit/job name often differs from pkg name, e.g.
# bind9→named, apache2→apache2, postgresql-NN→postgresql@NN-main):
systemctl list-unit-files | grep -i docker | head

On bionic the standard archive no longer ships security fixes. Verify Ubuntu Pro ESM coverage:

# Ubuntu Pro CLI is the standard tool:
sudo pro status --format=json 2>/dev/null | head
apt-cache policy | grep -i esm

Step-by-Step Diagnosis

1. List failing services.

   systemctl --failed --no-pager

2. Tail the journal / syslog for docker-registry.

   sudo journalctl -u docker-registry -f --no-pager
   sudo journalctl -xe -f --no-pager

3. Inspect UFW (Uncomplicated Firewall) state.

   sudo ufw status numbered
   sudo ufw show added
   sudo iptables -L -n -v | head -30

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

   sudo journalctl -k 2>/dev/null | grep -i 'apparmor="DENIED"' | tail -30
   sudo aa-status
   # /etc/apparmor.d/usr.bin.docker-registry or usr.sbin.docker-registry — inspect first
   sudo aa-complain /etc/apparmor.d/usr.bin.docker-registry 2>/dev/null || true

5. Verify docker-registry integrity and reinstall if anything is altered.

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

6. Correlate findings with /var/log/apt/history.log, /var/log/dpkg.log, and Ubuntu Security Notice USN-6336-1 to pin the change that introduced the regression.

Solution – Primary Fix

Apply the corrective apt transaction referenced by Ubuntu Security Notice USN-6336-1, then reload the affected service:

sudo apt update
sudo apt -y install --only-upgrade docker-registry
sudo systemctl daemon-reload
# Service name may differ from pkg name; check first:
systemctl list-unit-files | grep -i docker | head
sudo systemctl restart docker-registry
dpkg -l docker-registry | tail -1            # confirm new version
systemctl is-active docker-registry

On bionic the standard archive is past EoL for security; enable Ubuntu Pro ESM to receive the fix:

# Standard pro CLI:
sudo pro attach <token>
sudo pro enable esm-infra
sudo pro enable esm-apps
sudo apt update
sudo apt -y install --only-upgrade docker-registry

For kernel / glibc / systemd / openssl advisories a reboot (or Livepatch) is required:

sudo apt install -y needrestart
sudo needrestart -r l       # list units that need restart
sudo systemctl reboot       # or: sudo shutdown -r now
# Livepatch (Ubuntu Pro) avoids reboot for many kernel CVEs:
sudo canonical-livepatch status
sudo canonical-livepatch refresh

Solution – Alternative Approaches

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

• Hold the package so apt cannot upgrade it:

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

• Pin a known-good version via apt preferences:

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

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

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

• Investigate AppArmor blocking the new binary; switch to complain briefly, capture denials, then re-enforce:

  sudo aa-complain /etc/apparmor.d/usr.bin.docker-registry 2>/dev/null
  # reproduce the failure
  sudo journalctl -k | grep apparmor | tail
  sudo aa-enforce /etc/apparmor.d/usr.bin.docker-registry 2>/dev/null

• Apply Canonical Livepatch (Ubuntu Pro) to land kernel fixes without reboot:

  sudo canonical-livepatch status
  sudo canonical-livepatch refresh

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

  sudo apt -y install --only-upgrade -t bionic-security docker-registry

Verification & Acceptance Criteria

All of these should pass after the fix is applied:

dpkg -l docker-registry | tail -1                                  # expected fixed version
apt list --upgradable 2>/dev/null | grep -i security || echo OK
systemctl is-active docker-registry
sudo journalctl -u docker-registry --since "5 minutes ago" --no-pager | grep -iE "error|fail" || echo OK
sudo ufw status numbered | head
sudo aa-status 2>/dev/null | head -5

The conditions described in the advisory must no longer be reported for docker-registry 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
# ZFS-on-root (Ubuntu 20.04+ default installer option):
sudo zfs snapshot rpool/ROOT/ubuntu@pre-docker-registry
# LVM-on-root:
sudo lvcreate -L 4G -s -n root_pre_patch /dev/<vg>/<root-lv>

To revert:

sudo apt install --allow-downgrades -y docker-registry=<old-version>
sudo systemctl daemon-reload
sudo systemctl restart docker-registry
# Kernel rollback: pick the prior kernel from the GRUB menu, then:
sudo systemctl reboot
# ZFS rollback (rolls the whole root dataset):
sudo zfs rollback -r rpool/ROOT/ubuntu@pre-docker-registry

Prevention & Hardening

Reduce the chance of this recurring on Ubuntu 18.04 (bionic):

• Enable scheduled security updates via unattended-upgrades:

  sudo apt install -y unattended-upgrades update-notifier-common
  sudo dpkg-reconfigure -plow unattended-upgrades
  # /etc/apt/apt.conf.d/50unattended-upgrades:
  Unattended-Upgrade::Allowed-Origins { "${distro_id}:${distro_codename}-security"; };

• Install needrestart so services restart automatically after library upgrades:

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

• Attach Ubuntu Pro for ESM (mandatory on this past-EoL release) and Livepatch where supported:

  sudo pro attach <token>
  sudo pro enable esm-infra
  sudo pro enable esm-apps
  sudo pro enable livepatch

• Subscribe to ubuntu-security-announce and watch ubuntu.com/security/cves.

• Monitor file integrity with debsums and AIDE:

  sudo apt install -y debsums aide
  sudo debsums -ca
  sudo aideinit && sudo mv /var/lib/aide/aide.db.new /var/lib/aide/aide.db
  sudo aide --check

• For estate-wide patching, manage with Canonical Landscape:

  sudo apt install -y landscape-client
  sudo landscape-config

• Keep AppArmor profiles in enforce mode and apply CIS Ubuntu Linux Benchmark hardening.

Related Errors & Cross-Refs

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

sudo dpkg --configure -a
sudo apt --fix-broken install
systemd-analyze critical-chain
sudo journalctl -k 2>/dev/null | grep -i apparmor | tail
cat /proc/sys/kernel/tainted

View all ubuntu-18-04 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

Primary reference: Ubuntu Security Notice USN-6336-1. Manual pages useful on Ubuntu 18.04:

man apt
man apt-get
man apt-mark
man dpkg
man systemctl
man journalctl
man ufw
man apparmor
man aa-status
man unattended-upgrades
man canonical-livepatch
man pro

Other resources: Ubuntu Security Notices, Ubuntu CVE Tracker, Ubuntu upgrade notes, and per-package notes in /usr/share/doc/docker-registry/ for components implicated in this advisory.