📖 ~4 min read • Source: FreeBSD VuXML
VuXML topic: graylog — remote code execution in log4j from user-controlled log input
Related CVEs: CVE-2021-44228 CVE-2021-45046
Upstream summary: Apache Software Foundation reports: It was found that the fix to address CVE-2021-44228 in Apache Log4j 2.15.0 was incomplete in certain non-default configurations. This could allows attackers with control over Thread Context Map (MDC) input data when the logging configuration uses a non-default Pattern Layout with either a Context Lookup (for example, $${ctx:loginId}) or a Thread Context Map pattern (%X, %mdc, or %MDC) to craft malicious input data using a JNDI Lookup patter
Table of contents
Symptom & Impact
graylog runs as a long-lived process on FreeBSD 15, started at boot and holding open sockets (visible in ss -lntp), so a flaw in it stays reachable for as long as the service is up. Exploitation usually means code execution in the daemon’s own security context, memory disclosure from a process holding credentials and cached client data, or a crash that takes the listener down. Workers started before the upgrade keep running the old binary until the service is restarted. graylog is a genuine long-running service, so restart steps do apply — but confirm the service name first with service -e | grep graylog, since it often differs from the package name (bind ships named).
Environment & Reproduction
Reproduction targets FreeBSD 15. Confirm with freebsd-version -kru, uname -a, and the installed package via pkg info graylog and pkg query "%n-%v" graylog. Capture system state with pkg audit -F and service -e. Trigger the workflow that exposes graylog 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 The FreeBSD ports security team shipped a corrective graylog port revision; hosts on an outdated build remain exposed.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: service graylog-server status, tail -100 /var/log/messages, pkg audit -F, pkg version -v graylog, 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 graylog for integrity. 5) pkg install -fy graylog 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 graylog port revision referenced by FreeBSD VuXML. Typical commands: sudo pkg update, sudo pkg upgrade graylog (or sudo pkg upgrade -y for the whole system), then sudo service graylog-server restart, and pkg audit to confirm no remaining advisories. For ports tree builders: sudo portsnap fetch update + cd /usr/ports/<cat>/graylog && 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 graylog 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 graylog shows the expected fixed version, service graylog-server status is running, pkg audit returns no advisory for graylog, tail -50 /var/log/messages shows no errors after restart, and the original reproduction for graylog 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-graylog-patch. To revert, run sudo pkg install -f <previous-version> or boot the previous BE via bectl activate pre-graylog-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 graylog: 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.
