📖 ~4 min read • Source: FreeBSD VuXML
VuXML topic: Kubectl — Potential directory traversal
Related CVEs: CVE-2019-1002101
Upstream summary: Kubernetes.io reports: A security issue was discovered with the Kubernetes kubectl cp command that could enable a directory traversal replacing or deleting files on a user’s workstation.
Table of contents
Symptom & Impact
kubectl 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 FreeBSD 15 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. kubectl 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 kubectl itself.
Environment & Reproduction
Reproduction targets FreeBSD 15. Confirm with freebsd-version -kru, uname -a, and the installed package via pkg info kubectl and pkg query "%n-%v" kubectl. Capture system state with pkg audit -F and service -e. Trigger the workflow that exposes kubectl while collecting tail -200 /var/log/messages, dmesg -a, and /var/log/pkg.log.
Root Cause Analysis
Root cause is tracked at FreeBSD VuXML. The FreeBSD ports security team shipped a corrective kubectl port revision; hosts on an outdated build remain exposed. Correlate /var/log/pkg.log with /var/log/messages and kernel state in sysctl kern.lastpid + sysctl kern.osreldate to isolate the change that triggered the failure mode.
Quick Triage
Quick triage: tail -100 /var/log/messages, pkg audit -F, pkg version -v kubectl, and pfctl -sr (or ipfw list) to confirm firewall posture. For kernel issues: dmesg -a | tail -100 and kldstat.
Step-by-Step Diagnosis
1) service -e to enumerate failed services. 2) tail -F /var/log/messages and dmesg. 3) Validate firewall via pfctl -sr -v or ipfw show. 4) pkg check -B kubectl for integrity. 5) pkg install -fy kubectl to reinstall if tampered. 6) Correlate findings with /var/log/pkg.log and FreeBSD VuXML to pin the commit that introduced the regression.
Solution – Primary Fix
Primary fix: install the corrective kubectl port revision referenced by FreeBSD VuXML. Typical commands: sudo pkg update, sudo pkg upgrade kubectl (or sudo pkg upgrade -y for the whole system), then and pkg audit to confirm no remaining advisories. For ports tree builders: sudo portsnap fetch update + cd /usr/ports/<cat>/kubectl && sudo make deinstall reinstall clean. Reboot if the kernel module is involved.
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Solution – Alternative Approaches
Alternatives include locking the package with sudo pkg lock kubectl until vetted, downgrading via pkg install <older-version> from a pinned repo, switching the FreeBSD pkg repository between quarterly and latest in /usr/local/etc/pkg/repos/FreeBSD.conf, isolating the affected service in a jail (iocage/bastille) with stricter firewall rules, or replacing the service with a vendored static build for the period between exposure detection and full rollout.
Verification & Acceptance Criteria
Acceptance: pkg info kubectl shows the expected fixed version is running, pkg audit returns no advisory for kubectl, tail -50 /var/log/messages shows no errors after restart, and the original reproduction for kubectl no longer triggers across two consecutive runs.
Rollback Plan
Capture state with pkg query "%n-%v" > /root/pkg-pre.txt and a ZFS boot-environment snapshot: bectl create pre-kubectl-patch. To revert, run sudo pkg install -f <previous-version> or boot the previous BE via bectl activate pre-kubectl-patch && reboot. For kernel/loader changes, drop to the loader prompt and select the previous boot environment.
Prevention & Hardening
Prevent recurrence by scheduling pkg audit -F via periodic.conf (daily_status_security_pkgaudit_enable="YES"), subscribing to freebsd-security-notifications, mirroring through a local pkg repo managed by poudriere, version-pinning sensitive packages with pkg lock, enabling automatic ZFS BE snapshots before upgrades, and monitoring file integrity via mtree or aide. Apply the CIS FreeBSD hardening checklist where applicable and harden jails with allow.* tunables in /etc/jail.conf.
Related Errors & Cross-Refs
Related issues that commonly surface alongside kubectl: pkg lock contention, mismatched ABI after kernel/userland skew (freebsd-version vs uname -K), pf rule drift, and stale shared-library references after upgrade (pkg check -d).
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References & Further Reading
Primary reference: FreeBSD VuXML. Supporting docs: FreeBSD Handbook, man pkg, man freebsd-update, man pfctl, man ipfw, man bectl, man periodic.conf, the FreeBSD Security Advisories at security.freebsd.org, and /usr/ports/UPDATING for port-specific notes implicated in this advisory.
