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CVE-2026-63913 is a state-transition validation flaw in the Linux kernel's Netfilter TCP connection-tracking implementation. After observing a SYN packet, the vulnerable logic can transition a conntrack entry to TCP_CONNTRACK_CLOSE upon receiving an RST with an invalid sequence number, without checking the expected reply direction or confirming that a matching SYN was sent in the opposite direction. A crafted SYN followed by an invalid-sequence RST can prematurely terminate an active NAT entry and disrupt its associated TCP connection. The vulnerability is associated with the broader NatJack NAT-state manipulation attack class.
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20 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A Linux kernel netfilter TCP connection-tracking flaw permits a crafted SYN followed by an invalid-sequence RST to prematurely close an active NAT entry. The state machine fails to verify packet direction and a corresponding SYN before transitioning to CLOSE. The reference assigns a CVSS v3 base score of 8.2, with potential integrity and availability impacts, although vendor severity is LOW.
A Linux kernel vulnerability addressed by an AlmaLinux 9 kernel update; no flaw-specific technical detail is supplied.
A vulnerability addressed by the Rocky Linux 9 kernel update; technical details are not provided.
A Linux kernel Netfilter conntrack TCP state-handling flaw involving invalid-sequence RST packets and direction checks.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.