Overview
- Anthropic disclosed on October 27 that its Claude model produced an exploit that achieved remote root command execution in tests against servers running Multipath TCP (MPTCP) listeners.
- The flaw is an IPv4 TCP race condition that can cause a use-after-free when the kernel hands IP option memory to a new socket without copying it, allowing attackers to leak kernel memory and corrupt a callback pointer.
- Kernel developers fixed the bug upstream on October 5 and backported the patch to maintained stable branches, but distribution updates are uneven with Debian, Oracle, SUSE and some Amazon kernels patched while Ubuntu and Red Hat had not published fixes as of October 29–30.
- Anthropic said the exploit works in two stages—first leaking a kernel address to defeat KASLR, then overwriting a callback to run a payload—and that successful tests required many attempts and about 48–53 minutes to reach command execution.
- Administrators should install vendor or backported kernel updates where available, limit access to exposed TCP services, consider blocking IPv4 TCP packets with IP options, and note that enabling MPTCP by default in some software such as Go 1.24 can increase exposure; there are no confirmed in-the-wild attacks so far.