Ubuntu 24.04 — fonttools — multiple vulnerabilities (2 CVEs) — patch and remediation guide

📖 ~4 min read  •  Source: Ubuntu Security Notice USN-7917-1

Related CVEs: CVE-2025-66034 CVE-2023-45139

Upstream summary: It was discovered that the subsetting module of fontTools was vulnerable to
an XML External Entity (XEE) attack. An unauthenticated remote attacker
could possibly use this issue to include arbitrary files from the file
system or make web requests from the host system. This issue only affected
Ubuntu 22.04 LTS. (CVE-2023-45139)

It was discovered that fontTools was vulnerable to path traversal attacks.
If a user or automated system were tricked into extracting a specially
cra

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 Ubuntu 24.04 (noble) hosts that have fonttools installed, administrators report behaviour consistent with Ubuntu Security Notice USN-7917-1: apt reports pending security updates, services backed by fonttools fail or restart unexpectedly, AppArmor denials appear in the kernel log, 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 fonttools sits on the serving path.

Environment & Reproduction

Reproduction targets Ubuntu 24.04 (noble). Confirm release and installed package:

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

Trigger the workflow that exposes fonttools — multiple vulnerabilities (2 CVEs) — patch and remediation guide while collecting:

sudo journalctl -u fonttools -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-7917-1. Canonical security maintainers shipped fixes in the corresponding fonttools update for Ubuntu 24.04; running an outdated build leaves the host exposed to the failure modes described in the advisory. Fixes land in the noble-security pocket of the main archive. Correlate apt history with the journal:

grep -A2 -B2 fonttools /var/log/apt/history.log
zgrep -A2 -B2 fonttools /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 24.04 to capture the current state of fonttools:

dpkg -l fonttools | tail -1                  # installed version
dpkg -V fonttools                             # verify shipped files
sudo apt update && apt list --upgradable 2>/dev/null | grep -i security
systemctl is-active fonttools
sudo ufw status verbose 2>/dev/null | head -20
sudo aa-status 2>/dev/null | head -20
# If fonttools 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 fonttools | head

Step-by-Step Diagnosis

1. List failing services.

   systemctl --failed --no-pager

2. Tail the journal / syslog for fonttools.

   sudo journalctl -u fonttools -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.fonttools or usr.sbin.fonttools — inspect first
   sudo aa-complain /etc/apparmor.d/usr.bin.fonttools 2>/dev/null || true

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

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

6. Correlate findings with /var/log/apt/history.log, /var/log/dpkg.log, and Ubuntu Security Notice USN-7917-1 to pin the change that introduced fonttools — multiple vulnerabilities (2 CVEs) — patch and remediation guide.

Solution – Primary Fix

Apply the corrective apt transaction referenced by Ubuntu Security Notice USN-7917-1, then reload the affected service:

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

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

• Pin a known-good version via apt preferences:

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

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

  apt-cache madison fonttools
  sudo apt install --allow-downgrades -y fonttools=<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.fonttools 2>/dev/null
  # reproduce the failure
  sudo journalctl -k | grep apparmor | tail
  sudo aa-enforce /etc/apparmor.d/usr.bin.fonttools 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 noble-security fonttools

Verification & Acceptance Criteria

All of these should pass after the fix is applied:

dpkg -l fonttools | tail -1                                  # expected fixed version
apt list --upgradable 2>/dev/null | grep -i security || echo OK
systemctl is-active fonttools
sudo journalctl -u fonttools --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 original reproduction for fonttools — multiple vulnerabilities (2 CVEs) — patch and remediation guide must not trigger 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-fonttools
# LVM-on-root:
sudo lvcreate -L 4G -s -n root_pre_patch /dev/<vg>/<root-lv>

To revert:

sudo apt install --allow-downgrades -y fonttools=<old-version>
sudo systemctl daemon-reload
sudo systemctl restart fonttools
# 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-fonttools

Prevention & Hardening

Reduce the chance of this recurring on Ubuntu 24.04 (noble):

• 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 to enable Livepatch and extended security coverage:

  sudo pro attach <token>
  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 fonttools — multiple vulnerabilities (2 CVEs) — patch and remediation guide: 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-24-04 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

Primary reference: Ubuntu Security Notice USN-7917-1. Manual pages useful on Ubuntu 24.04:

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/fonttools/ for components implicated in fonttools — multiple vulnerabilities (2 CVEs) — patch and remediation guide.