Linux kernel netfilter flowtable action count validation flaw
CVE-2026-43329 is a Linux kernel vulnerability in the netfilter flowtable hardware offload path caused by insufficient enforcement of the maximum number of flow actions. The issue arises because certain IPv6 flowtable offload combinations can require more actions than the implementation previously allowed. The documented IPv6 case can reach 17 actions: ethernet mangling consumes 4 payload actions, SNAT 4, DNAT 4, double VLAN/QinQ handling 4 VLAN actions, and redirect 1, already exceeding the prior limit of 16; act_ct may also add tunnel-related actions. Because payload actions operate on 32-bit words, IPv6 address mangling requires 4 payload actions per address operation. The fix updates flow_action_entry_next() call sites to strictly check the maximum number of supported actions and increases the per-flow action limit from 16 to 24.
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Exploits
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No public exploit code observed for this vulnerability.
Affected products & vendors
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Recent activity
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The version that knows your environment.
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Every observed campaign linking this CVE to a named adversary.
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Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.