SLES 15 — libXext6 — vulnerability — patch and remediation guide

📖 ~4 min read  •  Source: SUSE advisory SUSE-SU-2013:1099-1 (see also SUSE bugzilla)

Related CVEs: CVE-2013-1982

Upstream summary: Multiple integer overflows in X.org libXext 1.3.1 and earlier allow X servers to trigger allocation of insufficient memory and a buffer overflow via vectors related to the (1) XcupGetReservedColormapEntries, (2) XcupStoreColors, (3) XdbeGetVisualInfo, (4) XeviGetVisualInfo, (5) XShapeGetRectangles, and (6) XSyncListSystemCounters functions.

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

Nothing executes libXext6 on its own; its code runs inside whatever links against or imports it, so the exposed surface on a SLES 15 host is the union of every process that has loaded it — web workers, cron jobs, mail handlers, backup agents. The package manager replaces the files on disk, but processes already running keep the old build mapped, and virtualenvs, vendored copies and container images each carry their own copy, so a host can report itself patched while still running vulnerable code. libXext6 is a library — code loaded by other programs rather than a daemon — so there is no unit to restart and systemctl status libXext6 will simply report no such unit; restart its consumers instead.

Environment & Reproduction

Reproduction targets SLES 15. Confirm release, registration, and installed package:

cat /etc/os-release
SUSEConnect --status-text
SUSEConnect --list-extensions 2>/dev/null | head -30
rpm -q libXext6
zypper info libXext6 | head -20

Exercise the workload that uses libXext6 while collecting:

sudo zypper ps  # NATIVE SUSE TOOL, no extra package: every running process still using deleted/replaced files, plus the owning service name
sudo zypper ps -s  # short table (PID, PPID, UID, login, command, service) without the per-file detail
sudo zypper ps -sss  # service names ONLY, one per line - safe to pipe straight into systemctl
sudo journalctl -xe --no-pager | tail -200
sudo tail -200 /var/log/zypp/history
sudo tail -200 /var/log/audit/audit.log
# For SUSE support, bundle evidence with supportconfig:
sudo supportconfig -R /var/tmp -B libXext6

Root Cause Analysis

Root cause is documented in SUSE advisory SUSE-SU-2013:1099-1. SUSE security maintainers shipped fixes in the corresponding libXext6 update for SLES 15; running an outdated build leaves the host exposed to the failure modes described in the advisory. Correlate zypper history with system logs:

sudo zypper history | grep libXext6
sudo zypper history --since='-7 days' | tail -40
sudo journalctl -k | grep -i apparmor | tail -100
cat /proc/sys/kernel/tainted   # non-zero = tainted kernel / out-of-tree modules

Quick Triage

Run these on SLES 15 to capture the current state of libXext6:

rpm -q libXext6                              # installed NVR
rpm -V libXext6                              # verify shipped files
sudo zypper patch-check                    # open patches
sudo zypper lp -r SUSE-SLE-Server-15-* 2>/dev/null | head
systemctl --failed --no-pager
sudo firewall-cmd --list-all
sudo aa-status                              # AppArmor profiles
rpm -ql libXext6 | grep -E '^/(usr/lib|etc)/systemd/(system|user)/[^/]+\.(service|socket|timer|path|target|mount)$'  # the units libXext6 REALLY ships - NO OUTPUT means it ships no service at all, so never run systemctl on it
rpm -ql libXext6 | grep -E '^/usr/sbin/rc[^/]+$'  # SUSE-only rcNAME compat symlink (it points at /usr/sbin/service, not at a unit): the NAME after 'rc' IS the service name - bind ships /usr/sbin/rcnamed, so the unit is named.service

Step-by-Step Diagnosis

1. List failed systemd units.

   systemctl --failed --no-pager

2. Tail the journal for libXext6 and the system bus.

   sudo journalctl -xe -f --no-pager

3. Inspect firewall posture (firewalld is the default on SLES 15+).

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

4. Surface AppArmor denials and switch the profile to complain mode if needed.

   sudo journalctl -k | grep -i 'apparmor="DENIED"' | tail -30
   sudo aa-status

5. Verify libXext6 integrity and reinstall if anything is altered.

   sudo rpm -V libXext6
   sudo zypper verify
   sudo zypper install --force libXext6

6. Correlate findings with /var/log/zypp/history, zypper history, and SUSE advisory SUSE-SU-2013:1099-1 to pin the change that introduced the regression.

Solution – Primary Fix

Apply the corrective zypper transaction referenced by SUSE advisory SUSE-SU-2013:1099-1, then reload affected systemd units:

sudo zypper ref                        # refresh repos
sudo zypper -n patch                   # apply ALL open patches (recommended)
# Or target a single package:
sudo zypper -n update libXext6
sudo systemctl daemon-reload
# Unit name may differ from pkg name; check first:
sudo systemctl daemon-reload  # load unit files replaced by the update; this alone restarts nothing
sudo systemctl restart UNIT1.service UNIT2.service  # restart several in ONE transaction - systemd applies their own After=/Before= ordering, so low-level units (dbus, database, broker) go before their consumers
sudo systemctl restart UNIT.service  # NOTE: 'systemctl reload' is NOT enough after a library patch - the process must re-exec to map the new .so
sudo systemctl reload apparmor.service  # only if 'rpm -ql libXext6 | grep /etc/apparmor.d/' showed the package ships AppArmor profiles
rpm -q libXext6                           # confirm new NVR

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

sudo zypper ps -s                      # services using deleted libs
sudo systemctl reboot                  # or: sudo shutdown -r now
# SUSE Live Patching (kgraft / klp) avoids reboot for kernel CVEs:
sudo zypper install -y kernel-livepatch-$(uname -r | tr - _)
klp -v patches                         # active livepatches

Solution – Alternative Approaches

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

• Roll back via Snapper (Btrfs snapshots taken automatically before zypper transactions on SLES 15):

  sudo snapper list
  sudo snapper undochange <pre>..<post>  # diff between two snapshot numbers
  sudo snapper rollback <pre>            # boot the host into the chosen snapshot

• Lock the package so zypper cannot upgrade it:

  sudo zypper al libXext6                   # add lock
  zypper ll | grep libXext6                 # list locks
  sudo zypper rl libXext6                   # remove lock

• Install an older NVR if a regression is suspected:

  zypper se -s libXext6                     # show all available versions
  sudo zypper install --oldpackage libXext6-<older-NVR>

• Disable the AppArmor profile briefly to confirm policy is the cause, then re-enable:

  # reproduce, capture denials in the journal:
  sudo journalctl -k | grep apparmor | tail

• Where SLE Live Patching is licensed, apply kernel fixes without reboot:

  klp -v patches                         # active livepatches
  sudo zypper install -y kernel-livepatch-$(uname -r | tr - _)

Verification & Acceptance Criteria

All of these should pass after the fix:

rpm -q libXext6                                            # expected fixed NVR
sudo zypper patch-check                                  # 0 critical patches outstanding
sudo firewall-cmd --list-services
sudo aa-status | head -5
sudo zypper ps -s                                        # any services still using deleted libs

The conditions described in the advisory must no longer be reported for libXext6 across two consecutive runs.

Rollback Plan

Capture state before any change:

rpm -qa > /root/rpm-pre.txt
sudo zypper history list > /root/zypper-history-pre.txt
# Snapper takes pre/post snapshots automatically on Btrfs root.
sudo snapper create -d 'pre-patch-libXext6'   # explicit named snapshot
sudo snapper list | head

To revert if the patch is bad:

# Preferred on Btrfs root — boot the prior snapshot:
sudo snapper rollback <snapshot-id>
sudo systemctl reboot
# Or downgrade just the package:
sudo zypper install --oldpackage libXext6-<older-NVR>
sudo systemctl daemon-reload
# Custom security policy cleanup:

Prevention & Hardening

Reduce the chance of this recurring on SLES 15:

• Enable automatic patch installation:

  sudo zypper install -y zypper-automatic
  sudo systemctl enable --now zypper-automatic.timer
  # Or use YaST: yast2 online_update_configuration

• Subscribe to sle-security-updates and watch suse.com/support/update.

• Mirror through SUSE Manager or RMT (Repository Mirroring Tool) for controlled rollouts:

  sudo zypper install -y rmt-server rmt-cli
  sudo rmt-cli sync
  sudo rmt-cli products enable SLES/15/x86_64

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

  sudo zypper al libXext6

• Ensure Snapper is enabled on the root subvolume and pre/post hooks run for every zypper transaction:

  sudo snapper -c root get-config | head
  # Default zypper plugin: /usr/lib/zypp/plugins/commit/snapper.zypp-commit-plugin

• Monitor file integrity with AIDE:

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

• Subscribe to SUSE Live Patching so kernel CVEs can be remediated without reboot:

  sudo SUSEConnect -p sle-module-live-patching/15.0/x86_64
  sudo zypper install -y kernel-livepatch-$(uname -r | tr - _)
  klp -v patches

• Keep AppArmor profiles in enforce; review /etc/apparmor.d/ after every package upgrade.

• Apply CIS SUSE Linux Enterprise Server Benchmark hardening.

Related Errors & Cross-Refs

Issues that commonly surface alongside a libXext6 update: zypper lock contention, systemd unit ordering cycles, AppArmor denials, firewalld zone drift, and kernel taint flags. Useful triage:

sudo zypper ps -s
systemd-analyze critical-chain
sudo journalctl -k | grep apparmor | tail
sudo firewall-cmd --get-active-zones
cat /proc/sys/kernel/tainted

View all sles-15 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

Primary reference: SUSE advisory SUSE-SU-2013:1099-1 (see also SUSE bugzilla). Manual pages useful on SLES 15:

man zypper
man zypper.conf
man systemctl
man journalctl
man firewall-cmd
man snapper
man apparmor
man aa-status
man SUSEConnect
man klp

Other resources: SUSE Linux Enterprise Server 15 documentation, suse.com/security, SUSE security blog, and per-package notes in /usr/share/doc/packages/libXext6/ for components implicated in this advisory.