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 __nf_conncount_add() 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
nf_ct_zone_id() and nf_ct_zone_equal(), passing conn->zone.dir or
zone->dir as the direction argument.
Those helpers take enum ip_conntrack_dir values: IP_CT_DIR_ORIGINAL is 0
and IP_CT_DIR_REPLY is 1. However, zone->dir is a u8 bitmask:
NF_CT_ZONE_DIR_ORIG is 1, NF_CT_ZONE_DIR_REPL is 2 and
NF_CT_DEFAULT_ZONE_DIR 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
nf_ct_zone_id() can fall back to NF_CT_DEFAULT_ZONE_ID instead of using
the real zone id, so different zones can be treated as equal and dedup
collapses to tuple equality alone.
nf_conncount stores and compares the original-direction tuple for a
connection. If an skb already has an attached conntrack entry,
get_ct_or_tuple_from_skb() explicitly copies
ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple, regardless of the packet's
ctinfo. Therefore the zone comparison in the tuple dedup path must use
IP_CT_DIR_ORIGINAL 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 IP_CT_DIR_ORIGINAL directly.
Do not special-case NF_CT_DEFAULT_ZONE_DIR and do not compare raw zone
ids: using the existing helpers with IP_CT_DIR_ORIGINAL preserves the
direction-aware NF_CT_DEFAULT_ZONE_ID 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.
netfilter: nf_conncount: fix zone comparison in tuple dedup
The "already exists" dedup logic in __nf_conncount_add() 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
nf_ct_zone_id() and nf_ct_zone_equal(), passing conn->zone.dir or
zone->dir as the direction argument.
Those helpers take enum ip_conntrack_dir values: IP_CT_DIR_ORIGINAL is 0
and IP_CT_DIR_REPLY is 1. However, zone->dir is a u8 bitmask:
NF_CT_ZONE_DIR_ORIG is 1, NF_CT_ZONE_DIR_REPL is 2 and
NF_CT_DEFAULT_ZONE_DIR 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
nf_ct_zone_id() can fall back to NF_CT_DEFAULT_ZONE_ID instead of using
the real zone id, so different zones can be treated as equal and dedup
collapses to tuple equality alone.
nf_conncount stores and compares the original-direction tuple for a
connection. If an skb already has an attached conntrack entry,
get_ct_or_tuple_from_skb() explicitly copies
ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple, regardless of the packet's
ctinfo. Therefore the zone comparison in the tuple dedup path must use
IP_CT_DIR_ORIGINAL 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 IP_CT_DIR_ORIGINAL directly.
Do not special-case NF_CT_DEFAULT_ZONE_DIR and do not compare raw zone
ids: using the existing helpers with IP_CT_DIR_ORIGINAL preserves the
direction-aware NF_CT_DEFAULT_ZONE_ID 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.
Metrics
Affected Vendors & Products
Advisories
No advisories yet.
Fixes
Solution
No solution given by the vendor.
Workaround
No workaround given by the vendor.
References
History
Sat, 15 Aug 2026 06:00:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | 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 __nf_conncount_add() 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 nf_ct_zone_id() and nf_ct_zone_equal(), passing conn->zone.dir or zone->dir as the direction argument. Those helpers take enum ip_conntrack_dir values: IP_CT_DIR_ORIGINAL is 0 and IP_CT_DIR_REPLY is 1. However, zone->dir is a u8 bitmask: NF_CT_ZONE_DIR_ORIG is 1, NF_CT_ZONE_DIR_REPL is 2 and NF_CT_DEFAULT_ZONE_DIR 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 nf_ct_zone_id() can fall back to NF_CT_DEFAULT_ZONE_ID instead of using the real zone id, so different zones can be treated as equal and dedup collapses to tuple equality alone. nf_conncount stores and compares the original-direction tuple for a connection. If an skb already has an attached conntrack entry, get_ct_or_tuple_from_skb() explicitly copies ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple, regardless of the packet's ctinfo. Therefore the zone comparison in the tuple dedup path must use IP_CT_DIR_ORIGINAL 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 IP_CT_DIR_ORIGINAL directly. Do not special-case NF_CT_DEFAULT_ZONE_DIR and do not compare raw zone ids: using the existing helpers with IP_CT_DIR_ORIGINAL preserves the direction-aware NF_CT_DEFAULT_ZONE_ID 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. | |
| Title | netfilter: nf_conncount: fix zone comparison in tuple dedup | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
|
|
Projects
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MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-08-15T05:54:35.201Z
Reserved: 2026-08-09T03:40:39.914Z
Link: CVE-2026-72247
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-08-15T06:21:51.887
Modified: 2026-08-15T06:21:51.887
Link: CVE-2026-72247
Redhat
No data.
OpenCVE Enrichment
No data.
Weaknesses
No weakness.