Debian 11 — kubernetes — multiple vulnerabilities (20 CVEs) — patch and remediation guide

📖 ~4 min read  •  Source: Debian Security Tracker

Related CVEs: CVE-2016-7075 CVE-2017-1000056 CVE-2017-1002101 CVE-2017-1002102 CVE-2018-1002100 CVE-2018-1002102 CVE-2018-1002105 CVE-2019-1002100  +12 more

Upstream summary: It was found that Kubernetes as used by Openshift Enterprise 3 did not correctly validate X.509 client intermediate certificate host name fields. An attacker could use this flaw to bypass authentication requirements by using a specially crafted X.509 certificate.

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

kubernetes 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 Debian 11 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. kubernetes 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 kubernetes itself.

Environment & Reproduction

Reproduction targets Debian 11 (bullseye). Confirm release and installed package:

cat /etc/debian_version
lsb_release -a 2>/dev/null || cat /etc/os-release
dpkg -l kubernetes | tail -2
apt-cache policy kubernetes
dpkg-query -W -f='${Status}\n' kubernetes

Exercise the workload that uses kubernetes while collecting:

needrestart -b -r l  # (pkg: needrestart) run as root; machine-readable. NEEDRESTART-SVC = units still mapping deleted libs, NEEDRESTART-SESS = login sessions, NEEDRESTART-KSTA = kernel state. -r l never restarts anything
needrestart -v -l -r l  # human-readable, libraries only (-l); names each PID and the obsolete file it still maps
checkrestart -v  # (pkg: debian-goodies) older alternative; add -p to report only deleted files owned by a dpkg package, -m for machine-readable
sudo journalctl -xe --no-pager | tail -200
sudo tail -200 /var/log/apt/history.log
sudo tail -200 /var/log/dpkg.log

Root Cause Analysis

Root cause is tracked at Debian Security Tracker. The Debian Security Team shipped fixes in the corresponding kubernetes point release for Debian 11 (suite bullseye-security); running an outdated build leaves the host exposed to the failure modes referenced above. Correlate apt history with the journal:

grep -A2 -B2 kubernetes /var/log/apt/history.log
zgrep -A2 -B2 kubernetes /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 Debian 11 to capture the current state of kubernetes:

dpkg -l kubernetes | tail -1                   # installed version
dpkg -V kubernetes                              # verify shipped files
sudo apt update && apt list --upgradable 2>/dev/null | grep -i security
systemctl --failed --no-pager
sudo nft list ruleset 2>/dev/null | head -50
sudo aa-status 2>/dev/null | head -20      # AppArmor profiles
dpkg-query -L kubernetes 2>/dev/null | grep -E '^/etc/init\.d/[^/]+$'  # legacy SysV init script; its basename is the service name for 'service <name> restart' on non-systemd hosts
systemctl list-unit-files --no-pager --type=service,socket,timer | grep -iF -- 'kubernetes'  # fuzzy name match; -F is required because package names contain regex metacharacters ('+' in libstdc++6/g++-13 makes -E fail to match at all)

Step-by-Step Diagnosis

1. List failed systemd units.

   systemctl --failed --no-pager

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

   sudo journalctl -xe -f --no-pager

3. Inspect firewall state (this OS defaults to nftables).

   sudo nft list ruleset
   sudo nft list tables

4. Verify kubernetes file integrity and reinstall if anything is altered.

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

5. Check AppArmor denials (Debian 11+ default-enabled).

   sudo journalctl -k | grep -i 'apparmor="DENIED"' | tail -30
   sudo aa-status | grep -i kubernetes

6. Correlate findings with /var/log/apt/history.log, /var/log/dpkg.log, and Debian Security Tracker to pin the change that introduced the regression.

Solution – Primary Fix

Apply the corrective apt transaction documented in Debian Security Tracker from the security suite, then reload the affected unit:

sudo apt update
sudo apt -y install --only-upgrade kubernetes
sudo systemctl daemon-reload
# Unit name may differ from package name; check first:
dpkg-query -W -f='${Package} ${Version}\n' kubernetes; gcc --version | head -1; ld --version | head -1; as --version | head -1  # record the FIXED toolchain version you are rebuilding with (ld/as come from binutils)
ccache -C && ccache -s  # (pkg: ccache) MUST clear the cache, or the rebuild silently reuses object files produced by the vulnerable compiler and you ship the bug again
make clean; cmake --build build --target clean; ninja -C build -t clean; cargo clean; go clean -cache  # drop stale objects before rebuilding (use whichever applies to the project)
dpkg -l kubernetes | tail -1                # confirm new version

For kernel / glibc / systemd / openssl advisories a reboot is required:

sudo apt install -y needrestart
sudo needrestart -r l       # list services that need restart
sudo systemctl reboot       # or: sudo shutdown -r now

Solution – Alternative Approaches

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

• Pin a known-good version via apt preferences:

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

• Mark the package on hold so apt cannot upgrade it:

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

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

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

• Switch firewall backend between iptables-legacy and nftables (Debian 10+):

  sudo update-alternatives --config iptables
  sudo update-alternatives --config ip6tables
  sudo systemctl restart netfilter-persistent 2>/dev/null

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

  # /etc/apt/sources.list.d/bullseye-security-only.list
  deb http://security.debian.org/debian-security bullseye-security main contrib non-free
  # then:
  sudo apt update && sudo apt -y install --only-upgrade -t bullseye-security kubernetes

• Investigate AppArmor blocking the new binary; switch the profile to complain mode briefly:

  # reproduce, capture denials, then re-enforce:

Verification & Acceptance Criteria

All of these should pass after the fix is applied:

dpkg -l kubernetes | tail -1                                  # expected fixed version
apt list --upgradable 2>/dev/null | grep -i security || echo OK
sudo nft list ruleset | head
sudo aa-status 2>/dev/null | head -5

The conditions described in the advisory must no longer be reported for kubernetes 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
# LVM snapshot of the root LV (only if root sits on LVM):
sudo lvcreate -L 4G -s -n root_pre_patch /dev/<vg>/<root-lv>

To revert:

sudo apt install --allow-downgrades -y kubernetes=<old-version>
sudo systemctl daemon-reload
# If a kernel was rolled back, reboot and select the previous kernel from GRUB:
sudo systemctl reboot
# LVM snapshot merge (offline / on next reboot):
sudo lvconvert --merge /dev/<vg>/root_pre_patch

Prevention & Hardening

Reduce the chance of this recurring on Debian 11:

• Enable scheduled security updates via unattended-upgrades:

  sudo apt install -y unattended-upgrades apt-listchanges
  sudo dpkg-reconfigure -plow unattended-upgrades
  # /etc/apt/apt.conf.d/50unattended-upgrades:
  Unattended-Upgrade::Origins-Pattern { "origin=Debian,codename=${distro_codename},label=Debian-Security"; };

• Install needrestart so services restart automatically after library upgrades:

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

• Subscribe to debian-security-announce and watch security-tracker.debian.org.

• Mirror locally for controlled rollouts:

  sudo apt install -y apt-mirror
  # /etc/apt/mirror.list:
  deb http://deb.debian.org/debian bullseye main contrib non-free
  deb http://security.debian.org/debian-security bullseye-security main contrib non-free
  sudo apt-mirror

• Monitor file integrity with debsums and AIDE:

  sudo apt install -y debsums aide
  sudo debsums -ca           # report only changed conffile-less files
  sudo aideinit && sudo mv /var/lib/aide/aide.db.new /var/lib/aide/aide.db
  sudo aide --check

• Apply CIS Debian Linux Benchmark hardening and review auditd rules in /etc/audit/rules.d/.

Related Errors & Cross-Refs

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

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

View all debian-11 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

Primary reference: Debian Security Tracker. Manual pages useful on Debian 11:

man apt
man apt-get
man apt-mark
man dpkg
man systemctl
man journalctl
man nft
man apparmor
man unattended-upgrades

Other resources: The Debian Administrator’s Handbook, Debian Security FAQ, Debian Security Tracker, and per-package notes in /usr/share/doc/kubernetes/ for components implicated in this advisory.