Oracle Linux 9 — bind — vulnerability — patch and remediation guide (ELSA-2025-19951)

📖 ~4 min read  •  Source: ELSA advisory ELSA-2025-19951

Related CVEs: CVE-2025-40778 CVE-2025-40780

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

bind runs as a long-lived process on Oracle Linux 9, 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 unit is reloaded or restarted. bind is a genuine long-running service, so restart steps do apply — but confirm the unit name first with systemctl list-unit-files | grep -i bind, since it often differs from the package name (bind ships named.service).

Environment & Reproduction

Reproduction targets Oracle Linux 9 running either the Red Hat Compatible Kernel (RHCK) or the Unbreakable Enterprise Kernel (UEK). Confirm release, kernel, and installed package:

cat /etc/oracle-release
uname -r
rpm -q bind
dnf list installed bind
dnf history list --reverse | head -20

Exercise the workload that uses bind while collecting:

journalctl -u named -b --no-pager | tail -200
journalctl -xe --no-pager | tail -200
tail -200 /var/log/dnf.log
tail -200 /var/log/audit/audit.log

Root Cause Analysis

Root cause is documented in ELSA advisory ELSA-2025-19951. Upstream Red Hat / Oracle Linux maintainers shipped a fix in the corresponding bind errata; running an outdated build leaves the host exposed and may trigger the failure modes described in the advisory. Correlate transaction history with system logs and SELinux audit entries to isolate the originating change:

dnf history list --reverse | head -30
dnf history info $(dnf history list | awk '/bind/ {print $1; exit}')
ausearch -m AVC,USER_AVC -ts today | tail -100
cat /proc/sys/kernel/tainted   # non-zero = kernel modules / out-of-tree drivers loaded

Quick Triage

Run these checks on Oracle Linux 9 to confirm the failure mode and current state of bind:

rpm -q bind                              # installed version
rpm -V bind                              # verify file integrity
dnf updateinfo info --security bind     # any security advisories outstanding
systemctl --failed --no-pager
firewall-cmd --list-all 2>/dev/null || echo 'firewalld not running'
getenforce                                 # SELinux mode
# bind runs as the "named" service - restart it once the upgrade is in place:
# e.g. httpd pkg/unit match, but bind→named, postgresql-server→postgresql):
systemctl list-unit-files | grep -i bind | head -5

Step-by-Step Diagnosis

1. List failed units.

   systemctl --failed --no-pager

2. Follow the journal for bind and the system bus.

   journalctl -u named -f --no-pager
   journalctl -xe -f --no-pager

3. Check firewall posture (skip if firewalld is masked).

   firewall-cmd --list-all-zones --permanent
   nft list ruleset 2>/dev/null | head -50

4. Surface SELinux denials and translate them to a policy module if needed.

   ausearch -m AVC,USER_AVC -ts today
   ausearch -m AVC -ts today | audit2allow -a -M /tmp/local-fix
   # Inspect /tmp/local-fix.te before applying:
   sudo semodule -i /tmp/local-fix.pp

5. Verify bind integrity and dependency closure.

   dnf check
   rpm -V bind
   rpm -q --requires bind | xargs -r rpm -q --whatprovides | head

6. Correlate findings with /var/log/dnf.log, dnf history and ELSA advisory ELSA-2025-19951 to pin the change that introduced the regression.

Solution – Primary Fix

Apply the corrective dnf transaction referenced by ELSA advisory ELSA-2025-19951, reload affected systemd units, and reconcile firewalld / SELinux state:

sudo dnf clean expire-cache
sudo dnf -y update bind
sudo systemctl daemon-reload
# bind runs as the "named" service - restart it once the upgrade is in place:
sudo systemctl restart named
rpm -q bind                       # confirm new NVR
systemctl is-active named          # confirm running (if a unit exists)

If the advisory says a reboot is required (kernel, glibc, systemd, openssl):

sudo needs-restarting -r           # reports kernel/init/glibc need
sudo systemctl reboot              # or: sudo shutdown -r now

Solution – Alternative Approaches

If the primary fix is not viable, choose from these alternatives:

• Roll back the offending dnf transaction:

  sudo dnf history list --reverse
  sudo dnf history undo <id>

• Pin bind with the versionlock plugin:

  sudo dnf install -y python3-dnf-plugin-versionlock
  sudo dnf versionlock add bind
  sudo dnf versionlock list | grep bind

• Downgrade to a known-good NVR from the repo cache or vault:

  sudo dnf --showduplicates list bind
  sudo dnf -y downgrade bind-<older-NVR>

• Switch firewalld backend (nftables ↔ iptables) for compatibility:

  sudo sed -i 's/^FirewallBackend=.*/FirewallBackend=iptables/' /etc/firewalld/firewalld.conf
  sudo systemctl restart firewalld

• If SELinux is suspected, switch to permissive briefly, capture denials, and author a custom module before re-enforcing:

  sudo setenforce 0                                    # do NOT leave permissive
  # reproduce the failure
  sudo ausearch -m AVC -ts recent | audit2allow -a -M mylocal
  sudo semodule -i mylocal.pp
  sudo setenforce 1

• Where the advisory has Ksplice coverage, live-patch without reboot (Oracle Linux Premier Support):

  sudo uptrack-show                # current live patches
  sudo uptrack-upgrade -y          # apply all available
  uptrack-uname -r                 # effective kernel after live patching

Verification & Acceptance Criteria

All of these should pass after the fix:

rpm -q bind                                       # shows the expected fixed NVR
dnf updateinfo list --security installed | head    # no security advisories pending for us
systemctl is-active named 2>/dev/null              # active (if a unit exists)
journalctl -u named --since "5 minutes ago" --no-pager  # no new errors
firewall-cmd --list-services                        # required services present
getenforce                                          # intended mode (Enforcing/Permissive)

The conditions described in the advisory must no longer be reported for bind across two consecutive runs.

Rollback Plan

Capture state before any change:

rpm -qa > /root/rpm-pre.txt
dnf history list --reverse > /root/dnf-history-pre.txt
# LVM snapshot of the root LV (size to ~10% of root):
sudo lvcreate -L 4G -s -n root_pre_patch /dev/mapper/$(lvs --noheadings -o lv_path | grep -m1 root | xargs basename)

To revert if the patch is bad:

sudo dnf history undo <id>
# Or downgrade just bind to the previous NVR:
sudo dnf -y downgrade bind
sudo systemctl daemon-reload
# For SELinux module additions:
sudo semodule -r mylocal
# Reboot only if kernel/initramfs/glibc were rolled back:
sudo systemctl reboot

For kernel rollbacks, select the previous entry from the GRUB menu or set it as default with grubby --set-default /boot/vmlinuz-<older>.

Prevention & Hardening

Prevent recurrence on Oracle Linux 9 hosts running bind:

• Enable scheduled security updates via dnf-automatic:

  sudo dnf install -y dnf-automatic
  # Edit /etc/dnf/automatic.conf:
  # upgrade_type = security
  # apply_updates = yes
  sudo systemctl enable --now dnf-automatic.timer

• Subscribe to the Oracle Linux Errata RSS / mailing list at linux.oracle.com/security.

• Mirror through a local yum/dnf repository:

  sudo dnf install -y dnf-utils createrepo_c
  sudo reposync --download-metadata --downloadcomps -p /srv/repos -m --repo=ol9_baseos_latest
  sudo createrepo_c /srv/repos/ol-baseos

• Pin sensitive packages so they cannot be auto-upgraded:

  sudo dnf install -y python3-dnf-plugin-versionlock
  sudo dnf versionlock add bind

• Snapshot the root LV before every upgrade window:

  sudo lvcreate -L 4G -s -n root_pre_$(date +%Y%m%d) /dev/<vg>/<root-lv>

• Monitor file integrity with AIDE:

  sudo dnf install -y aide
  sudo aide --init && sudo mv /var/lib/aide/aide.db.new.gz /var/lib/aide/aide.db.gz
  sudo aide --check

• Lock down with SELinux audit rules in /etc/audit/rules.d/:

  # /etc/audit/rules.d/90-cp.rules
  -w /etc/passwd  -p wa -k identity
  -w /etc/shadow  -p wa -k identity
  -w /etc/sudoers -p wa -k privilege
  -a always,exit -F arch=b64 -S execve -k exec

• Where licensed, enable Oracle Ksplice for live kernel and userspace patching:

  sudo dnf install -y uptrack ksplice-tools
  sudo uptrack-upgrade -y
  sudo systemctl enable --now uptrack

Related Errors & Cross-Refs

Issues that commonly surface alongside a bind update: dnf transaction lock contention, systemd unit ordering cycles, SELinux AVC bursts, firewalld zone drift, and kernel taint flags. Triage with:

cat /proc/sys/kernel/tainted
systemd-analyze critical-chain
ausearch -m AVC -ts today | tail
firewall-cmd --get-active-zones
dnf history list --reverse | head

View all oracle-linux-9 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

Primary reference: ELSA advisory ELSA-2025-19951. Useful manual pages on Oracle Linux 9:

man dnf
man dnf.conf
man systemctl
man journalctl
man firewall-cmd
man semanage
man audit2allow
man grubby

Other resources: Oracle Linux 9 Administrator’s Guide at docs.oracle.com, the upstream Red Hat CVE database at access.redhat.com/security/cve, the Oracle Ksplice known-fixes feed, and /usr/share/doc/bind/ for component-specific notes implicated in bind.