📖 ~4 min read • Source: Debian Security Tracker
Related CVEs: CVE-2018-3979
Upstream summary: A remote denial-of-service vulnerability exists in the way the Nouveau Display Driver (the default Ubuntu Nvidia display driver) handles GPU shader execution. A specially crafted pixel shader can cause remote denial-of-service issues. An attacker can provide a specially crafted website to trigger this vulnerability. This vulnerability can be triggered remotely after the user visits a malformed website. No further user interaction is required. Vulnerable versions include Ubunt
Table of contents
Symptom & Impact
Nothing executes xserver-xorg-video-nouveau on its own; its code runs inside whatever links against or imports it, so the exposed surface on a Debian 13 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. xserver-xorg-video-nouveau is a library — code loaded by other programs rather than a daemon — so there is no unit to restart and systemctl status xserver-xorg-video-nouveau will simply report no such unit; restart its consumers instead.
Environment & Reproduction
Reproduction targets Debian 13. Confirm release with cat /etc/debian_version and lsb_release -a, and the currently installed package with dpkg -l xserver-xorg-video-nouveau and apt-cache policy xserver-xorg-video-nouveau. Capture system state with sudo reportbug xserver-xorg-video-nouveau if you need to file upstream. Trigger the workflow that exposes xserver-xorg-video-nouveau while collecting journalctl -b, /var/log/apt/history.log, and dpkg -l output.
Root Cause Analysis
Root cause is tracked at Debian Security Tracker. The Debian Security Team shipped fixes in the corresponding xserver-xorg-video-nouveau point release for Debian 13; running an outdated build leaves the host exposed to the failure modes referenced above. Correlate journalctl --since with apt history (/var/log/apt/history.log) and any kernel taint flags in /proc/sys/kernel/tainted to isolate the originating change.
Quick Triage
Quick triage: sudo apt update && apt list --upgradable, sudo nft list ruleset (or sudo iptables -L), and sudo dpkg --audit. For kernel issues review journalctl -k --since "1 hour ago".
Step-by-Step Diagnosis
1) systemctl --failed. 2) journalctl -xe and . 3) Validate firewall: sudo nft list ruleset or sudo iptables -L -n -v. 4) dpkg -V xserver-xorg-video-nouveau for integrity. 5) sudo apt install --reinstall xserver-xorg-video-nouveau if files were tampered. 6) Correlate findings with /var/log/apt/history.log, /var/log/dpkg.log, and Debian Security Tracker to pin the change that introduced the regression.
Solution – Primary Fix
Primary fix: apply the corrective apt transaction documented in Debian Security Tracker. Typical commands: sudo apt update, sudo apt -y install --only-upgrade xserver-xorg-video-nouveau (or sudo unattended-upgrade -v), then dpkg -l xserver-xorg-video-nouveau to validate the new build is installed. For kernel advisories add sudo reboot.
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Solution – Alternative Approaches
Alternatives include pinning a known-good version via /etc/apt/preferences.d/xserver-xorg-video-nouveau.pref, holding the package with sudo apt-mark hold xserver-xorg-video-nouveau, rolling back with sudo apt install xserver-xorg-video-nouveau=<old-version>, switching firewall backends between iptables-legacy and nftables via update-alternatives --config iptables, or applying the patch from the security archive only — deb debian-13-security main contrib non-free — while delaying the full point-release upgrade.
Verification & Acceptance Criteria
Acceptance: dpkg -l xserver-xorg-video-nouveau shows the expected fixed version is active shows no errors, apt list --upgradable no longer lists the advisory, sudo nft list ruleset matches the intended policy, and the original reproduction steps for xserver-xorg-video-nouveau no longer trigger the failure across two consecutive runs.
Rollback Plan
Capture state with apt list --installed > /root/apt-pre.txt and dpkg --get-selections > /root/dpkg-pre.txt. To revert, run sudo apt install --allow-downgrades xserver-xorg-video-nouveau=<old-version> and reload . Reboot if the kernel or initramfs changed and re-verify symptoms. Where LVM snapshots are in use, sudo lvconvert --merge /dev/<vg>/preupgrade is the fastest rollback path.
Prevention & Hardening
Prevent recurrence by enabling unattended-upgrades with Unattended-Upgrade::Origins-Pattern tuned to origin=Debian,codename=${distro_codename},label=Debian-Security, subscribing to debian-security-announce, mirroring through a local apt-mirror or aptly repo for controlled rollouts, version-locking sensitive packages, and monitoring file integrity with debsums -c or aide --check. Apply CIS Debian hardening and keep needrestart installed so service restarts happen automatically after library upgrades.
Related Errors & Cross-Refs
Related issues that commonly surface alongside xserver-xorg-video-nouveau: apt lock contention (dpkg --configure -a), systemd unit ordering cycles, firewall rule drift, and kernel taint flags in cat /proc/sys/kernel/tainted. See sibling common-problem articles in this Debian 13 series for adjacent failure modes.
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References & Further Reading
Primary reference: Debian Security Tracker. Supporting docs: Debian Administrators Handbook, man apt, man systemctl, man nft, man iptables, man journalctl, man debsums, the Debian Security Tracker at security-tracker.debian.org, and Debian Security FAQ at debian.org/security/faq. Review /usr/share/doc/xserver-xorg-video-nouveau/ for component-level notes implicated in xserver-xorg-video-nouveau.
