Linux Kernel Netfilter & io_uring Use-After-Free Local Privilege Escalation (CVE-2026-16003)

Affected Vendors

linux, ubuntu, redhat

Affected Components

linux-kernel, netfilter, io_uring

Published Date

2026-11-03

Executive & SecOps Summary

SECOPS ASSESSMENT

Affected Scope

Linux servers running Ubuntu, RHEL, Debian, or Rocky Linux across cloud and on-premise environments

Impact

Any low-privileged local user or compromised web service can escalate to full root privileges in milliseconds

Mitigation

Restrict unprivileged io_uring and user namespaces via sysctl immediately until kernel reboot windows are scheduled

Affected Products & Version Scope

Linux Kernel 6.1 LTS through 6.11 across Ubuntu 22.04/24.04, RHEL 9, and Debian 12

Remediation & Live Workaround Commands

PATCH & WORKAROUND

1. Live sysctl Mitigation (Zero Downtime) Block the exploit primitive immediately without rebooting production hosts:

bash

sudo sysctl -w kernel.io_uring_disabled=2
sudo sysctl -w kernel.unprivileged_userns_clone=0

echo "kernel.io_uring_disabled=2" | sudo tee -a /etc/sysctl.d/99-cve-mitigation.conf

2. Upgrade Kernel Packages Apply your distribution's patched kernel image during the next maintenance window.

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Technical Root Cause & Exploitation Mechanics

Root Cause Analysis (Use-After-Free / CWE-416) A race condition in reference counting between `io_uring` asynchronous callbacks and `nf_tables` transaction cleanup allows an attacker to trigger a Use-After-Free in kernel heap memory and overwrite `modprobe_path` or task credentials.

Official Vendor Advisories & References

NVD Original English Description

A use-after-free vulnerability in the Linux kernel netfilter and io_uring subsystem allows a local unprivileged user to escalate privileges to root.

https://nvd.nist.gov/vuln/detail/CVE-2026-16003

Source: NVD · Kernel Patch

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