Claude wrote a remote root exploit for a critical Linux kernel bug, and Ubuntu still has no patch
What's the deal? CVE-2026-98432, a use-after-free bug in the Linux kernel's IPv4 TCP handshake, is rated CVSS 9.8 (Critical) by the kernel's own CVE team. A remote attacker needs no login: the flaw sits in code every Linux server runs when it accepts an IPv4 TCP connection, before any application sees it. It dates back to Linux 4.4. The bug was reported by Xinyang Ge of Anthropic, and in a 27 October research post Anthropic said that, "after initial prompting", Claude wrote an exploit that runs "arbitrary commands as root, without any credentials or user interaction" on Linux servers with a multipath TCP listener. In its proof of concept, leaking a kernel pointer took 48 minutes and reaching command execution another five.
Who's patched? The upstream fix, a small change by kernel networking maintainer Eric Dumazet, shipped in stable kernels on 11 and 15 October. Debian, SUSE, Oracle and Amazon Linux have fixed kernels. Red Hat raised its rating from Important to Critical on 30 October and shipped fixes for RHEL 8, 9 and 10 on 1 November, though OpenShift's RHEL CoreOS is still listed as affected. As of 1 November, Canonical's Ubuntu tracker still showed every release as vulnerable, according to a running breakdown by Atlas Security. The Go Security Team warned that Go programs have opened multipath TCP listeners by default since Go 1.24, and that systems without them may still be exposed to similar attacks.
How bad is it? Anthropic has not published the exploit, and CloudLinux said its kernel team could not reproduce the remote-root claim. AWS says it is not aware of exploitation in the wild, and the bug is not in CISA's Known Exploited Vulnerabilities catalogue. But by 1 November, 41 GitHub repositories referenced the CVE, at least seven describing a race trigger or proof of concept. Shopify CEO Tobi Lütke shared the Atlas write-up with two words: "What a disaster." The post passed 2.5 million views.
The signal: AI models finding and weaponising bugs in core infrastructure is no longer hypothetical. The bottleneck now is how fast distributions ship fixes and how fast operators reboot into them.
Read more: Atlas Security, Anthropic, Red Hat RHSB-2026-016, Tobi Lütke (X)
Image credit: Atlas Security
