Mitigations for CVE-2026-98432 [IPv4 TCP handshake use-after-free]
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Summary
RODMENA Engineering describes CVE-2026-98432, a use-after-free in the IPv4 TCP handshake present in Linux since 4.4, with upstream fixes in stable branches from 5.10. Debian has patched kernels, while Ubuntu's were still pending on 1 November. Until then, the authors drop IPv4 TCP packets carrying IP options with nftables and disable MPTCP. Their tests showed plain connections passing and optioned ones timing out. The filter doesn't cover new network namespaces or containers. The claims come from the post itself, without independent sourcing, and Anthropic's reported exploit is unseen.