Bug 2516606 (CVE-2026-72320)

Summary: CVE-2026-72320 kernel: netfilter: nft_lookup: fix catchall element handling with inverted lookups
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Priority: high    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
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Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's `netfilter` component, specifically within the `nft_lookup` functionality. This issue arises from incorrect handling of 'catchall' elements during 'inverted lookups' in the `nft_lookup_eval()` function. Due to a logic error where the lookup result is not recomputed, network packets may be wrongly matched or skipped, leading to incorrect application of network filtering rules. This could potentially allow unauthorized network traffic or cause denial of service by incorrectly dropping legitimate traffic.
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Description OSIDB Bzimport 2026-08-15 06:21:34 UTC 
In the Linux kernel, the following vulnerability has been resolved:

netfilter: nft_lookup: fix catchall element handling with inverted lookups

nft_lookup_eval() decides whether a lookup matched (`found`) from the
direct set lookup and priv->invert before falling back to the
catchall element used by interval sets (e.g. nft_set_rbtree) for the
open-ended default range. Since `found` is never recomputed after
`ext` is replaced by the catchall lookup, inverted lookups
(NFT_LOOKUP_F_INV, "!= @set") can wrongly match or wrongly skip the
catchall element, producing the wrong verdict. Fold the catchall
lookup into `ext` before computing `found`, matching the order
already used by nft_objref_map_eval().
Comment 1 Keith Grant 2026-08-18 20:45:27 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026081506-CVE-2026-72320-23b8@gregkh/T