Linux kernel CVE-2026-98432: TCP use-after-free rated 9.8, Anthropic says its AI built a remote root exploit
Linux kernel (IPv4 TCP)
CVE-2026-98432 is a race-condition use-after-free in the Linux kernel's IPv4 TCP handshake code (ireq_opt/inet_opt freed without an RCU grace period), fixed upstream on Oct 15 and rated 9.8 by the kernel CNA. On Oct 28 Anthropic said an unreleased Claude model turned the bug into a zero-click remote root exploit against servers running a multipath TCP listener (about 48 minutes to defeat KASLR, five more to get a shell). The exploit was built in a lab and is not known to be used in attacks. Update to a fixed stable kernel.
Why this severity: CVSS 9.8 (kernel CNA); remote, no auth. Anthropic reports a lab-built root exploit; no known in-the-wild exploitation, not in CISA KEV.
- Started
- Oct 15, 2026
Affected
- Linux 4.4 and later stable branches before the fixed releases below
Fixed in
- 5.10.272
- 5.15.223
- 6.1.190
- 6.6.159
- 6.12.113
- 6.18.56
- 7.2.10
- 7.3
Timeline2
Anthropic's Frontier Red Team says an unreleased Claude model chained the bug into a zero-click remote root exploit on servers with a multipath TCP listener; the CVE record itself describes an IPv4 TCP fix, and only Anthropic's post links the two.
Fix ("ipv4: free inet_opt and ireq_opt after an RCU grace period") lands upstream and CVE-2026-98432 is published, rated 9.8 by the kernel CNA.
Advisories3
News & write-ups2
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