CVE-2026-98432
CVSS 9.8 CRITICAL: in the Linux kernel, the following vulnerability has been resolved: ipv4: free inet_opt and ireq_opt after an RCU… EPSS 0.4% (33rd percentile). Microsoft patch: Release Notes.
Vulnerabilities · 7h ago
Anthropic said October 27 that its model generated an exploit for Linux kernel TCP flaw CVE-2026-98432, which runs commands as root on servers with a multipath TCP (MPTCP) listener. As of October 29, Ubuntu and Red Hat Enterprise Linux had not shipped fixed kernels, though some other distributions had.
During an IPv4 TCP handshake, Linux can pass connection options to a new socket without copying them. If that socket is destroyed while another CPU is still reading the options, the kernel accesses memory already freed. The fix delays freeing until those reads finish; Anthropic says exploitation can yield root-level command execution.
The MPTCP link appears in Anthropic’s account, not the CVE record or kernel fix, leaving the reported exposure scope unconfirmed by those sources. Ubuntu and RHEL users depend on their distribution’s kernel packages for the upstream fix, so exposure differs by distribution and kernel variant.
CVSS 9.8 CRITICAL: in the Linux kernel, the following vulnerability has been resolved: ipv4: free inet_opt and ireq_opt after an RCU… EPSS 0.4% (33rd percentile). Microsoft patch: Release Notes.
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Linux Kernel TCP Flaw With 9.8 CVSS Score Affects Ubuntu, Red Hat and Other Distributions
Ubuntu and RHEL lack fixes for a Linux TCP use-after-free that Anthropic says it exploited to run commands as root on MPTCP servers.
Part of the PlainSec briefing for 2026-10-29