In the Linux kernel, the following vulnerability has been resolved:
netfilter: nf_conncount: fix zone comparison in tuple dedup
The "already exists" dedup logic in __nfconncountadd() decides whether a connection has already been counted and can be skipped instead of incrementing the connlimit count. It compares the conntrack zone of a list entry with the zone of the connection being added using nfctzoneid() and nfctzoneequal(), passing conn->zone.dir or zone->dir as the direction argument.
Those helpers take enum ipconntrackdir values: IPCTDIRORIGINAL is 0 and IPCTDIRREPLY is 1. However, zone->dir is a u8 bitmask: NFCTZONEDIRORIG is 1, NFCTZONEDIRREPL is 2 and NFCTDEFAULTZONEDIR is 3. Passing that bitmask as the enum direction shifts the meaning of every non-zero value. An ORIG-only zone passes 1 and is tested as REPLY, while REPL-only and default zones pass 2 or 3 and test bits beyond the valid direction range. In those cases nfctzoneid() can fall back to NFCTDEFAULTZONE_ID instead of using the real zone id, so different zones can be treated as equal and dedup collapses to tuple equality alone.
nfconncount stores and compares the original-direction tuple for a connection. If an skb already has an attached conntrack entry, getctortuplefromskb() explicitly copies ct->tuplehash[IPCTDIRORIGINAL].tuple, regardless of the packet's ctinfo. Therefore the zone comparison in the tuple dedup path must use IPCTDIRORIGINAL as well; the zone direction bitmask describes where a zone id applies, not which direction this conncount tuple represents.
Fix the two dedup comparisons by passing IPCTDIRORIGINAL directly. Do not special-case NFCTDEFAULTZONEDIR and do not compare raw zone ids: using the existing helpers with IPCTDIRORIGINAL preserves the direction-aware NFCTDEFAULTZONEID fallback. A default bidirectional zone contains the ORIG bit, so it naturally returns the real zone id; reply-only zones continue to fall back for original-direction tuple comparisons.
{
"cna_assigner": "Linux",
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/72xxx/CVE-2026-72247.json"
}