Remote code execution on Linux systems with multipath TCP

On October 27, LLM provider Anthropicreportedon aremotely exploitable use-after-free bug affecting systems withmultipath TCP listeners open. The bug works by triggering a response to aretransmitted SYN packet at the same moment that the TCP connection isestablished in another thread, causing the first thread to access theconnection's options structure after the second thread has freed it. The firstthread can then disclose kernel memory or cause a buffer overflow, writing anattacker-controlled payload. The fix wasto only free the structure after an RCU grace period.On October 29, the Go security teamadvisedthat all programs written in Go use multipath TCP by default, so manysystems may be unknowingly vulnerable. And, of course, there is always thepossibility of related bugs in other sections of the TCP stack. Users may bewise to update to a patched kernel as soon as one becomes available for theirdistribution.