Claude discovers a severe Linux kernel vulnerability that lay dormant for 11 years and generates a working exploit
Anthropic's Claude model discovered a use-after-free (UAF) flaw in the Linux kernel's IPv4 TCP handshake. The code was submitted in October 2015 and introduced with Linux 4.4; an attacker can trigger remote root privilege execution through network traffic without a password or user interaction. Claude also generated a working two-stage exploit: the first stage took about 48 minutes to defeat kernel address space layout randomization protections, and the second stage took only 5 minutes to execute arbitrary commands with root privileges. The whole process took about 53 minutes, and a failure does not cause the target to crash. The upstream fix was completed on October 15, covering 5.10.272, 6.1.190, 6.12.113, 6.18.56, 7.2.10, and 7.3-rc7, but as of November 1, Ubuntu 22.04 LTS, 24.04 LTS, 26.04 LTS, and 26.10 are still marked as affected, and the fix is still under development.
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The original text provides the root cause of the vulnerability, the time required for exploitation, and the scope of patch coverage, so readers can use it to assess the exposure window in Ubuntu environments.
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The root cause of the vulnerability is a use-after-free (UAF) flaw in the IPv4 TCP handshake. The code was submitted in October 2015 and introduced with the Linux 4.4 kernel; when handling TCP connection retransmissions, one CPU may read memory that another CPU has already freed.
An attacker needs no password and no user interaction—only network traffic—to trigger it, and can then achieve remote root-level code execution. The kernel CVE team classified it as a critical vulnerability that is network-reachable, requires no privileges, and requires no interaction.
Even more alarming is the role AI played in this. Anthropic's Claude model not only discovered the vulnerability but also generated a working two-stage exploit. The first stage took about 48 minutes and defeated kernel address space layout randomization; the second stage took only 5 minutes to execute arbitrary commands with root privileges. The entire attack process took about 53 minutes, and a failed exploit does not crash the target, so an attacker can retry repeatedly.
The upstream fix was completed on October 15, covering versions 5.10.272, 6.1.190, 6.12.113, 6.18.56, 7.2.10, and 7.3-rc7. Distributions such as Debian, Red Hat, and Amazon Linux have been releasing patches one after another.
But Ubuntu's situation is entirely different: as of November 1, Ubuntu 22.04 LTS, 24.04 LTS, 26.04 LTS, and 26.10 are still marked as affected, and fixes are still in development.
For Ubuntu administrators running externally facing services, the risk window remains open. Go 1.24 and later enable Multipath TCP by default on Linux, which may expand the exposure surface of this vulnerability, but disabling MPTCP can only reduce the risk and cannot eliminate the flaw at the kernel level.
Anthropic says the exploit code has not been publicly released, but this incident has clearly demonstrated a trend: AI is no longer just a tool for writing code—it can also become a weapon for breaking down a system's defenses.