Ubuntu 16.04 — python-urllib3 — multiple vulnerabilities (10 CVEs) — patch and remediation guide

📖 ~4 min read  •  Source: Ubuntu Security Notice USN-7599-1

Related CVEs: CVE-2025-50182 CVE-2025-50181 CVE-2024-37891 CVE-2018-25091 CVE-2023-43804 CVE-2023-45803 CVE-2020-26137 CVE-2018-20060  +2 more

Upstream summary: Jacob Sandum discovered that urllib3 handled redirects even when they were
explicitly disabled while using the PoolManager. An attacker could possibly
use this issue to obtain sensitive information. (CVE-2025-50181)

Illia Volochii discovered that urllib3 incorrectly handled retry and
redirect parameters when using Node.js. An attacker could possibly use this
issue to obtain sensitive information. This issue only affected Ubuntu
25.04. (CVE-2025-50182)

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 16.04 hosts running python-urllib3, administrators report behaviour consistent with Ubuntu Security Notice USN-7599-1: apt refusing to install or restart affected services, AppArmor denials in journalctl -k, and — for security-rated advisories — exposure to the vulnerability set above. In production estates the visible impact ranges from a single service restart to wider availability incidents whenever python-urllib3 sits on the serving path.

Environment & Reproduction

Reproduction targets Ubuntu 16.04. Confirm release with lsb_release -a and cat /etc/os-release, and the currently installed package with dpkg -l python-urllib3 and apt-cache policy python-urllib3. Capture system state with sudo ubuntu-bug python-urllib3 or sudo apport-collect for an evidence bundle. Trigger the workflow that exposes python-urllib3 — multiple vulnerabilities (10 CVEs) — patch and remediation guide while collecting journalctl -b, /var/log/apt/history.log, and dpkg -l output.

Root Cause Analysis

Root cause is documented in Ubuntu Security Notice USN-7599-1. Canonical security maintainers shipped fixes in the corresponding python-urllib3 update for Ubuntu 16.04; running an outdated build leaves the host exposed to the failure modes described in the advisory. Correlate journalctl --since timestamps with apt history (/var/log/apt/history.log) and any AppArmor denials in /var/log/syslog to isolate the originating change.

Quick Triage

Quick triage: run systemctl status python-urllib3, journalctl -u python-urllib3 -n 200, sudo apt update && apt list --upgradable, sudo ufw status verbose, and sudo aa-status. If AppArmor is in enforce mode, capture journalctl -k | grep apparmor to surface denials linked to python-urllib3 — multiple vulnerabilities (10 CVEs) — patch and remediation guide.

Step-by-Step Diagnosis

1) Confirm symptom with systemctl --failed. 2) Inspect logs: journalctl -xe and journalctl -u python-urllib3. 3) Validate firewall: sudo ufw status numbered. 4) Check AppArmor: sudo aa-status and journalctl -k | grep apparmor. 5) Verify package integrity: dpkg -V python-urllib3 and sudo apt install --reinstall python-urllib3. 6) Correlate findings with apt list --installed python-urllib3, /var/log/apt/history.log, and Ubuntu Security Notice USN-7599-1 to pin the change that introduced python-urllib3 — multiple vulnerabilities (10 CVEs) — patch and remediation guide.

Solution – Primary Fix

Primary fix for python-urllib3 — multiple vulnerabilities (10 CVEs) — patch and remediation guide: apply the corrective apt transaction described in Ubuntu Security Notice USN-7599-1, reload the affected systemd unit, and reconcile UFW / AppArmor state. Typical commands: sudo apt update, sudo apt -y install --only-upgrade python-urllib3 or sudo unattended-upgrade -v, sudo systemctl daemon-reload, sudo systemctl restart python-urllib3, then dpkg -l python-urllib3 to validate the new build is installed. For kernel advisories add sudo reboot or apply Ubuntu Livepatch (canonical-livepatch status) where covered by your Ubuntu Pro subscription.

Solution – Alternative Approaches

Alternatives include pinning a known-good version via /etc/apt/preferences.d/python-urllib3.pref with apt-mark hold python-urllib3, rolling back with sudo apt install python-urllib3=<old-version>, rotating UFW rules with sudo ufw reload, switching AppArmor profiles to complain mode (sudo aa-complain /etc/apparmor.d/usr.bin.python-urllib3) to confirm policy is the cause before authoring a custom profile, or applying Canonical Livepatch fixes via canonical-livepatch refresh where Ubuntu Pro is subscribed.

Verification & Acceptance Criteria

Acceptance: dpkg -l python-urllib3 shows the expected fixed version, systemctl is-active python-urllib3 returns active, journalctl -u python-urllib3 --since "5 minutes ago" shows no errors, apt list --upgradable no longer lists the advisory, sudo ufw status shows required services, sudo aa-status reports the intended profile mode, and the original reproduction steps for python-urllib3 — multiple vulnerabilities (10 CVEs) — patch and remediation guide no longer trigger the failure across two consecutive runs.

Rollback Plan

Capture state with apt list --installed > /root/apt-pre.txt, dpkg --get-selections > /root/dpkg-pre.txt, and where available sudo zfs snapshot rpool/ROOT/ubuntu@pre-python-urllib3 on ZFS-on-root installs. To revert, run sudo apt install --allow-downgrades python-urllib3=<old-version> and reload systemctl daemon-reload. Remove custom AppArmor profiles with sudo apparmor_parser -R. Reboot if the kernel or initramfs changed and re-verify symptoms.

Prevention & Hardening

Prevent recurrence by enabling unattended-upgrades with Unattended-Upgrade::Allowed-Origins tuned to ${distro_id}:${distro_codename}-security, subscribing to the ubuntu-security-announce mailing list, mirroring through Landscape / a local apt-mirror for controlled rollouts, version-locking sensitive packages, and monitoring file integrity with aide --check. Apply CIS Ubuntu hardening, keep AppArmor in enforce, and enable Canonical Livepatch under Ubuntu Pro so kernel advisories can be remediated without reboot.

Related Errors & Cross-Refs

Related issues that commonly surface alongside python-urllib3 — multiple vulnerabilities (10 CVEs) — patch and remediation guide: apt lock contention (dpkg --configure -a), systemd unit ordering cycles, AppArmor denials in journalctl -k, UFW zone drift, and kernel taint flags in cat /proc/sys/kernel/tainted. See sibling common-problem articles in this Ubuntu 16.04 series for adjacent failure modes.

View all ubuntu-16-04 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

Primary reference: Ubuntu Security Notice USN-7599-1. Supporting docs: Ubuntu Server Guide, man apt, man systemctl, man ufw, man aa-status, man apparmor, man journalctl, the Ubuntu CVE Tracker at ubuntu.com/security/cves, and Canonical Livepatch docs. Review /usr/share/doc/python-urllib3/ for component-level notes implicated in python-urllib3 — multiple vulnerabilities (10 CVEs) — patch and remediation guide.