Rocky Linux 10 — jq — multiple vulnerabilities (2 CVEs) — patch and remediation guide

📖 ~4 min read  •  Source: Rocky Linux RXSA RLSA-2026:16692

Related CVEs: CVE-2026-39979 CVE-2026-40164

Upstream summary: jq is a lightweight and flexible command-line JSON processor. jq is like sed for JSON data. You can use it to slice, filter, map, or transform structured data with the same ease that sed, awk, grep, or similar applications allow you to manipulate text.

Security Fix(es):

* jq: out-of-bounds read in jv_parse_sized() on error formatting for non-NUL-terminated buffers (CVE-2026-39979)

* jq: jq: Denial of Service via crafted JSON object causing hash collisions (CVE-2026-40164)

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 Rocky Linux 10 hosts that have jq installed, operators report behaviour consistent with Rocky Linux RXSA RLSA-2026:16692: dnf refuses to install or restart affected services, SELinux AVC denials appear in /var/log/audit/audit.log, and — for security-rated advisories — the host is exposed to the vulnerability set above. Impact ranges from a single service-restart loop to wider availability incidents whenever jq sits on the serving path.

Environment & Reproduction

Reproduction targets Rocky Linux 10. Confirm release and the installed package:

cat /etc/rocky-release
cat /etc/os-release
rpm -q jq
dnf info jq | head -20

Trigger the workflow that exposes jq — multiple vulnerabilities (2 CVEs) — patch and remediation guide while collecting:

sudo journalctl -u jq -b --no-pager | tail -200
sudo journalctl -xe --no-pager | tail -200
sudo tail -200 /var/log/dnf.log
sudo tail -200 /var/log/audit/audit.log
# For an evidence bundle bundle with sosreport:
sudo sosreport --batch

Root Cause Analysis

Root cause is documented in Rocky Linux RXSA RLSA-2026:16692. Rocky Linux / Red Hat maintainers shipped fixes in the corresponding jq update for Rocky Linux 10; running an outdated build leaves the host exposed to the failure modes described in the advisory. Correlate dnf history with system logs:

sudo dnf history | head
sudo dnf history list jq
sudo dnf history info <id>
sudo ausearch -m AVC,USER_AVC -ts today | tail -100
cat /proc/sys/kernel/tainted   # non-zero = tainted kernel / out-of-tree modules

Quick Triage

Run these on Rocky Linux 10 to capture the current state of jq:

rpm -q jq                              # installed NVR
rpm -V jq                              # verify shipped files
sudo dnf check-update --security
sudo dnf updateinfo list cves
systemctl --failed --no-pager
sudo firewall-cmd --list-all
getenforce && sestatus
# If jq ships a systemd unit (unit name may differ from pkg name, e.g.
# bind→named, postgresql-server→postgresql, php-fpm→php-fpm):
systemctl list-unit-files | grep -i jq | head

Step-by-Step Diagnosis

1. List failed systemd units.

   systemctl --failed --no-pager

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

   sudo journalctl -u jq -f --no-pager
   sudo journalctl -xe -f --no-pager

3. Inspect firewall posture.

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

4. Surface SELinux denials and author a local policy module if needed.

   sudo ausearch -m AVC,USER_AVC -ts today
   sudo ausearch -m AVC -ts today | audit2allow -a -M /tmp/local-fix
   sudo semodule -i /tmp/local-fix.pp

5. Verify jq integrity and reinstall if anything is altered.

   sudo rpm -V jq
   sudo dnf reinstall jq

6. Correlate findings with /var/log/dnf.log, dnf history, and Rocky Linux RXSA RLSA-2026:16692 to pin the change that introduced jq — multiple vulnerabilities (2 CVEs) — patch and remediation guide.

Solution – Primary Fix

Apply the corrective dnf transaction referenced by Rocky Linux RXSA RLSA-2026:16692, then reload affected systemd units:

sudo dnf -y makecache
sudo dnf -y upgrade --security              # apply ALL security errata (recommended)
# Or target a single package:
sudo dnf -y upgrade jq
sudo systemctl daemon-reload
# Unit name may differ from pkg name; check first:
systemctl list-unit-files | grep -i jq | head
sudo systemctl restart jq
rpm -q jq                                # confirm new NVR
systemctl is-active jq 2>/dev/null       # confirm running (if a unit exists)

For kernel / glibc / systemd / openssl advisories a reboot is required (or kpatch where licensed):

sudo needs-restarting -r                    # report whether reboot needed
sudo systemctl reboot                       # or: sudo shutdown -r now
# kpatch (Red Hat / Oracle) avoids reboot for many kernel CVEs:
sudo dnf install -y kpatch kpatch-dnf
sudo dnf kpatch auto                        # enable auto-patching
sudo kpatch list

Solution – Alternative Approaches

If the primary patch is not viable, choose from these:

• Roll back the offending dnf transaction:

  sudo dnf history list | head
  sudo dnf history info <id>
  sudo dnf history undo <id>

• Version-lock the package so dnf cannot upgrade it:

  sudo dnf install -y python3-dnf-plugin-versionlock
  sudo dnf versionlock add jq
  sudo dnf versionlock list
  sudo dnf versionlock delete jq      # remove the lock

• Install an older NVR if a regression is suspected:

  dnf --showduplicates list jq | tac | head
  sudo dnf install -y --allowerasing jq-<older-NVR>

• Switch SELinux to permissive briefly to confirm policy is the cause, then re-enforce:

  sudo setenforce 0
  # reproduce, capture denials, author a custom module:
  sudo ausearch -m AVC -ts recent | audit2allow -a -M mylocal
  sudo semodule -i mylocal.pp
  sudo setenforce 1

• Take an LVM snapshot before kernel / glibc upgrades for fast rollback:

  sudo lvs
  sudo lvcreate -s -n preupgrade -L 4G /dev/<vg>/<lv>
  # revert later via:
  sudo lvconvert --merge /dev/<vg>/preupgrade && sudo systemctl reboot

• Where kpatch is licensed, apply kernel fixes without reboot:

  sudo kpatch list
  sudo kpatch load /usr/lib/modules/$(uname -r)/extra/kpatch/*.ko

Verification & Acceptance Criteria

All of these should pass after the fix:

rpm -q jq                                            # expected fixed NVR
sudo dnf updateinfo list cves --installed               # CVEs above no longer listed
systemctl is-active jq 2>/dev/null
sudo journalctl -u jq --since "5 minutes ago" --no-pager | grep -iE "error|fail" || echo OK
sudo firewall-cmd --list-services
getenforce
sudo needs-restarting -r

The original reproduction for jq — multiple vulnerabilities (2 CVEs) — patch and remediation guide must not trigger across two consecutive runs.

Rollback Plan

Capture state before any change:

rpm -qa > /root/rpm-pre.txt
sudo dnf history list > /root/dnf-history-pre.txt
# Optional LVM snapshot of the root LV:
sudo lvcreate -s -n preupgrade -L 4G /dev/<vg>/<lv>

To revert if the patch is bad:

sudo dnf history undo <id>
# Or downgrade just the package:
sudo dnf install -y --allowerasing jq-<older-NVR>
sudo systemctl daemon-reload
sudo systemctl restart jq
# Or merge the LVM snapshot and reboot:
sudo lvconvert --merge /dev/<vg>/preupgrade && sudo systemctl reboot
# Custom SELinux policy cleanup:
sudo semodule -r mylocal

Prevention & Hardening

Reduce the chance of this recurring on Rocky Linux 10:

• Enable automatic security patching:

  sudo dnf install -y dnf-automatic
  sudo sed -i 's/^upgrade_type.*/upgrade_type = security/' /etc/dnf/automatic.conf
  sudo sed -i 's/^apply_updates.*/apply_updates = yes/' /etc/dnf/automatic.conf
  sudo systemctl enable --now dnf-automatic.timer

• Subscribe to rocky-announce and watch Red Hat security updates for upstream changes.

• Mirror through a local Pulp / Foreman / Spacewalk-style repo for controlled rollouts:

  sudo dnf install -y dnf-utils createrepo_c
  sudo reposync --download-metadata --downloadcomps -p /srv/mirror -- repoid=baseos
  sudo createrepo_c /srv/mirror/baseos

• Version-lock sensitive packages so they cannot be auto-upgraded:

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

• 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

• Enable kpatch so kernel CVEs can be remediated without reboot:

  sudo dnf install -y kpatch kpatch-dnf
  sudo dnf kpatch auto
  sudo kpatch list

• Keep SELinux in enforcing mode and review custom modules in /etc/selinux/targeted/ after every package upgrade.

• Apply CIS Rocky Linux 10 Benchmark hardening and remove unused packages.

Related Errors & Cross-Refs

Issues that commonly surface alongside jq — multiple vulnerabilities (2 CVEs) — patch and remediation guide: dnf lock contention, systemd unit ordering cycles, SELinux AVC bursts, firewalld zone drift, and kernel taint flags. Useful triage:

sudo dnf check
systemd-analyze critical-chain
sudo ausearch -m AVC -ts today | tail
sudo firewall-cmd --get-active-zones
cat /proc/sys/kernel/tainted
sudo needs-restarting -r

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References & Further Reading

Primary reference: Rocky Linux RXSA RLSA-2026:16692. Manual pages useful on Rocky Linux 10:

man dnf
man dnf.conf
man systemctl
man journalctl
man firewall-cmd
man semanage
man audit2allow
man kpatch
man sosreport

Other resources: docs.rockylinux.org, Red Hat CVE database, Rocky Linux errata, and per-package notes in /usr/share/doc/jq/ for components implicated in jq — multiple vulnerabilities (2 CVEs) — patch and remediation guide.

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