FreeBSD 12 — ghostscript7-korfont — vulnerability — patch and remediation guide

📖 ~4 min read  •  Source: FreeBSD VuXML

VuXML topic: ghostscript — exploitable buffer overflow in (T)BCP in PS interpreter

Related CVEs: CVE-2023-28879

Upstream summary: [email protected] reports: In Artifex Ghostscript through 10.01.0, there is a buffer overflow leading to potential corruption of data internal to the PostScript interpreter, in base/sbcp.c. This affects BCPEncode, BCPDecode, TBCPEncode, and TBCPDecode. If the write buffer is filled to one byte less than full, and one then tries to write an escaped character, two bytes are written.

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

ghostscript7-korfont ships data files, not a daemon — nothing on FreeBSD 12 listens on a socket because it is installed. The exposure lives in whatever reads those files: a font engine parsing glyph tables, a TLS library consulting the trust store, a runtime resolving a zone name. Symptoms are therefore indirect — a renderer or PDF job crashing on a malformed face, certificate validation accepting or rejecting the wrong issuer, timestamps and scheduled work landing an hour out after a rule change. Long-running processes keep the old copy cached until they are restarted. ghostscript7-korfont is a package of static data — fonts, certificates, timezone rules or documentation — read by other programs, so it has no service of its own to restart; the restarts that matter belong to its consumers.

Environment & Reproduction

Reproduction targets FreeBSD 12. Confirm release, installed package, and capture baseline state:

freebsd-version -kru
uname -a
pkg info ghostscript7-korfont
pkg query "%n-%v" ghostscript7-korfont
pkg audit -F
service -e

Exercise the workload that uses ghostscript7-korfont while collecting:

tail -200 /var/log/messages
dmesg -a | tail -200
tail -200 /var/log/pkg.log

Root Cause Analysis

Root cause is tracked at FreeBSD VuXML. The FreeBSD ports security team shipped a corrective ghostscript7-korfont port revision; hosts on an outdated build remain exposed. Correlate package logs with system logs and kernel state to isolate the change that triggered the failure mode:

tail -500 /var/log/pkg.log
tail -500 /var/log/messages
sysctl kern.lastpid
sysctl kern.osreldate     # numeric __FreeBSD_version, e.g. 1400097

Quick Triage

Run these checks on FreeBSD 12 to confirm the failure mode and current state of ghostscript7-korfont:

pkg version -v ghostscript7-korfont                # installed vs available version
pkg audit ghostscript7-korfont                     # advisory match for this package
tail -100 /var/log/messages
dmesg -a | tail -100
kldstat                              # kernel module state (for kernel/driver pkgs)
pfctl -sr 2>/dev/null || ipfw list   # only if pf/ipfw is enabled
# e.g. bind918→named, php83→php-fpm), check it:
pkg query '%Fp' ghostscript7-korfont | sed -n 's|.*/etc/rc\.d/||p'  # FreeBSD: the REAL service name(s) = basename of the rc.d script (bind918 -> named, postgresql16-server -> postgresql, apache24 -> apache24)
pkg query '%b' ghostscript7-korfont  # FreeBSD: shared libraries PROVIDED by ghostscript7-korfont. Non-empty here + no rc.d script = it is a library: patch it, then restart its consumers

Step-by-Step Diagnosis

1. List enabled services (only relevant if the package provides one).

   service -e

2. Follow live logs.

   tail -F /var/log/messages
   dmesg

3. Validate firewall rules (skip if neither pf nor ipfw is enabled).

   pfctl -sr -v 2>/dev/null || ipfw show

4. Check package integrity for ghostscript7-korfont.

   pkg check -B ghostscript7-korfont
   pkg check -d ghostscript7-korfont    # verify shared-library deps

5. Reinstall ghostscript7-korfont if integrity check fails.

   pkg install -fy ghostscript7-korfont

6. Correlate findings with /var/log/pkg.log and FreeBSD VuXML to pin the commit that introduced the regression.

Solution – Primary Fix

Install the corrective ghostscript7-korfont port revision referenced by FreeBSD VuXML:

sudo pkg update
sudo pkg upgrade ghostscript7-korfont              # or: sudo pkg upgrade -y for the whole system
pkg audit ghostscript7-korfont                    # confirm no remaining advisory for this package

For ports-tree builders (FreeBSD 13.x and earlier used portsnap; on FreeBSD 14+ the ports tree is fetched with Git):

# FreeBSD 14+ (portsnap was removed):
sudo pkg install -y git-lite
sudo git clone --depth 1 https://git.FreeBSD.org/ports.git /usr/ports
# FreeBSD 13.x and earlier:
# sudo portsnap fetch update
cd /usr/ports/<category>/ghostscript7-korfont
sudo make deinstall reinstall clean

Reboot only if the package ships a kernel module or replaces a shared library used by long-running daemons.

Solution – Alternative Approaches

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

• Lock the package until the fix is vetted:

  sudo pkg lock ghostscript7-korfont

• Downgrade to a known-good revision. pkg install pkgname-VERSION is not a real downgrade syntax — fetch a specific build instead:

  # 1. Discover available versions across configured repos:
  pkg search -e ghostscript7-korfont
  pkg rquery -r FreeBSD-quarterly '%n-%v' ghostscript7-korfont
  # 2. Install from a specific saved .pkg file:
  sudo pkg add -f /path/to/ghostscript7-korfont-<older-version>.pkg
  # 3. Or switch the host repo to the quarterly branch (see snippet below) and:
  sudo pkg upgrade -fr FreeBSD-quarterly ghostscript7-korfont

• Switch the pkg repository between quarterly and latest by editing /usr/local/etc/pkg/repos/FreeBSD.conf:

  FreeBSD: {
    url: "pkg+https://pkg.FreeBSD.org/${ABI}/quarterly",
    mirror_type: "srv",
    signature_type: "fingerprints",
    fingerprints: "/usr/share/keys/pkg",
    enabled: yes
  }

• Isolate the affected service in a jail with stricter firewall rules:

  iocage create -n ghostscript7-korfont-jail -r 12.4-RELEASE
  iocage set allow_raw_sockets=0 ghostscript7-korfont-jail
  # or with Bastille:
  bastille create ghostscript7-korfont-jail 12.4-RELEASE 10.0.0.10

• Replace the service with a vendored static build for the period between exposure detection and full rollout.

Verification & Acceptance Criteria

All of these should pass after the fix:

pkg info ghostscript7-korfont                # shows the expected fixed version
pkg audit ghostscript7-korfont               # no advisory for this package (exit code 0)
tail -50 /var/log/messages   # no new errors after upgrade
# If ghostscript7-korfont ships a service, confirm it is running under its rc.d name:

The conditions described in the advisory must no longer be reported for ghostscript7-korfont across two consecutive runs.

Rollback Plan

Capture state before any change (only ZFS root has boot environments — UFS hosts skip bectl):

pkg query "%n-%v" > /root/pkg-pre.txt
# ZFS-on-root only:
sudo bectl create pre-ghostscript7-korfont-patch

To revert if the upgrade is bad, reinstall the previously saved .pkg file:

sudo pkg add -f /var/cache/pkg/ghostscript7-korfont-<previous-version>.pkg
# Or activate the pre-patch boot environment and reboot (ZFS-on-root only):
sudo bectl activate pre-ghostscript7-korfont-patch
sudo shutdown -r now

For kernel/loader changes on a UFS host, boot the previous kernel from the loader prompt (press 3 at the menu, then boot kernel.old).

Prevention & Hardening

Prevent recurrence on FreeBSD 12 hosts running ghostscript7-korfont:

• Enable the daily security pkg audit in /etc/periodic.conf:

  daily_status_security_pkgaudit_enable="YES"

• Subscribe to freebsd-security-notifications at lists.freebsd.org.

• Mirror through a local pkg repository managed by poudriere:

  poudriere jail -c -j 12amd64 -v 12.4-RELEASE
  poudriere ports -c -p default
  poudriere bulk -j 12amd64 -p default <category>/ghostscript7-korfont

• Version-pin sensitive packages:

  sudo pkg lock ghostscript7-korfont

• Take an automatic ZFS boot-environment snapshot before every upgrade (ZFS root only):

  sudo bectl create pre-upgrade-$(date +%Y%m%d)

• Monitor file integrity (create a baseline, verify against it later):

  # Create a baseline (use -c; target /usr/local/etc, /etc, /boot — NOT /):
  sudo mtree -c -K sha256digest -p /usr/local/etc > /var/db/usr-local-etc.mtree
  sudo mtree -c -K sha256digest -p /etc          > /var/db/etc.mtree
  # Verify later:
  sudo mtree -p /usr/local/etc < /var/db/usr-local-etc.mtree
  # Or with AIDE for a richer ruleset:
  sudo pkg install -y aide && sudo aide --init && sudo aide --check

• Harden jails with allow.* tunables in /etc/jail.conf:

  ghostscript7-korfont_jail {
    allow.raw_sockets = 0;
    allow.sysvipc    = 0;
    allow.mount      = 0;
    allow.chflags    = 0;
  }

Related Errors & Cross-Refs

Issues that commonly surface alongside a ghostscript7-korfont update: pkg lock contention, mismatched ABI after kernel/userland skew, pf rule drift, and stale shared-library references after upgrade. Triage with:

freebsd-version -kru
uname -K
pkg check -d
pfctl -sr

View all freebsd-12 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

Primary reference: FreeBSD VuXML. Useful manual pages on FreeBSD 12:

man pkg
man freebsd-update
man pfctl
man ipfw
man bectl
man periodic.conf

Other resources: the FreeBSD Handbook, the FreeBSD Security Advisories at security.freebsd.org, and the /usr/ports/UPDATING file for port-specific notes implicated in this advisory.