A serious Linux Kernel TCP vulnerability, tracked as CVE-2026-98432, has raised concerns among cybersecurity experts. The Linux kernel’s CVE team has given it a critical CVSS score of 9.8 out of 10, making it a major security issue for Linux-based systems.
The vulnerability affects several Linux distributions, including Ubuntu, Red Hat Enterprise Linux (RHEL), and others. According to Anthropic, its AI model Claude successfully developed an exploit that could allow a remote attacker to execute commands with root-level access on certain Linux servers.
The issue is especially concerning because an attacker may not need login credentials to attempt exploitation.
How Does the Linux TCP Flaw Work?
The problem comes from a race condition in the Linux kernel’s IPv4 TCP connection-handling code. It can cause a use-after-free error, where the kernel tries to access memory that has already been released.
This issue occurs during the TCP handshake process. Under specific conditions, two processors may access the same memory at the wrong time, creating an opportunity for an attacker.
The vulnerability was introduced in Linux kernel version 4.4. IPv6 connections are not affected by this particular issue because the kernel handles their connection options differently.
Which Linux Distributions Are Affected?
Not every Linux distribution has released a security update yet. Some vendors have already fixed the issue, while others are still working on patches.
| Linux Distribution | Status as of October 29, 2026 |
|---|---|
| Ubuntu 22.04, 24.04, 26.04 and 26.10 | Fix in progress |
| Red Hat Enterprise Linux 8, 9 and 10 | Fix deferred |
| Amazon Linux 2023 | Some kernel packages fixed |
| Oracle Linux 7, 8, 9 and 10 | Fixed |
| Debian 12 and 13 | Fixed |
| SUSE Linux Micro 6.2 | Fixed |
| Some SUSE Enterprise releases | Testing or fix in progress |
The severity scores also differ between vendors. While the Linux kernel team assigned a 9.8 score, Red Hat rated it 5.9 on its CVE page. Oracle and SUSE assigned 8.1, while Amazon gave it 7.0.
These differences mainly come from how vendors assess the difficulty of successfully exploiting the race condition.
Anthropic Demonstrates a Root-Level Exploit
Anthropic reported that its Claude AI model created an exploit using the vulnerability. The attack works in two stages: first, it can expose kernel memory information, helping bypass Kernel Address Space Layout Randomization (KASLR). Then, it can overwrite a callback pointer and execute commands as root.
In Anthropic’s test, obtaining a kernel address took around 48 minutes, followed by another five minutes to achieve command execution.
However, the company did not publish the exploit code or all the tested system details. No confirmed in-the-wild attacks had been reported as of October 29, 2026.
How to Protect Your Linux System
System administrators should check their Linux distribution’s security advisories and install fixed kernel packages as soon as they become available.
Users running Debian, Oracle Linux, supported SUSE releases, and patched Amazon Linux kernels should apply the available updates. Ubuntu and RHEL administrators should closely monitor vendor announcements because fixes were still pending at the time of reporting.
The Linux Kernel TCP vulnerability is a reminder that even widely used operating systems can contain serious security flaws. Keeping kernel packages updated and monitoring official security notices remains essential for protecting Linux servers.
