high 7.5

CVE-2026-72247 json

netfilter: nf_conncount: fix zone comparison in tuple dedup

published 2026-08-15 2 mo ago modified 2026-10-16 23 d ago also EUVD-2026-59146

cvss: 7.5; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.7%; EPSS 0.7% chance of exploitation in 30 days, percentile 53%
public exploits: 0; none known

In the Linux kernel, the following vulnerability has been resolved:

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.

Patch / fix

fixed in 1 distros 4 links 8

Linux Linux 4.15, 5.10.261, 5.15.212, 6.1.178, 6.6.145, 6.12.97, 6.18.40, 7.1.5, 7.2

debian ubuntu suse opensuse

linux Debian 12 6.1.180-1
linux Debian 13 6.12.100-1
linux Debian 14 7.1.5-1

debian advisories DEBIAN-CVE-2026-72247

linux Ubuntu 22.04 LTS 5.15.0-198.208
linux Ubuntu 24.04 LTS 6.8.0-147.147
linux Ubuntu 26.04 LTS 7.0.0-38.38
linux-aws Ubuntu 22.04 LTS 5.15.0-1117.124
linux-aws Ubuntu 24.04 LTS 6.8.0-1067.70
linux-aws Ubuntu 26.04 LTS 7.0.0-1014.14
linux-gcp Ubuntu 22.04 LTS 5.15.0-1118.128
linux-gcp Ubuntu 24.04 LTS 6.8.0-1071.79

ubuntu advisories UBUNTU-CVE-2026-72247

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

kernel-64kb SLE Module for Basesystem 15 SP7 6.4.0-150700.53.84.1
kernel-syms SLE Module for Development Tools 15 SP7 6.4.0-150700.53.84.1
kernel-azure SLE Module for Public Cloud 15 SP7 6.4.0-150700.53.84.1
kernel-source SLE Module for Development Tools 15 SP7, SLE Module for Basesystem 15 SP7 6.4.0-150700.53.84.1
kernel-default SLE Workstation Extension 15 SP7, SLE Module for Legacy 15 SP7, SLE Module for Basesystem 15 SP7 +2 more 6.4.0-150700.53.84.1
kernel-zfcpdump SLE Module for Basesystem 15 SP7 6.4.0-150700.53.84.1
kernel-obs-build SLE Module for Development Tools 15 SP7 6.4.0-150700.53.84.1
kernel-default-base SLE Module for Basesystem 15 SP7 6.4.0-150700.53.84.1.150700.17.47.1

suse advisories SUSE-SU-2026:4706-1 SUSE-SU-2026:4640-1 SUSE-SU-2026:24316-1 SUSE-SU-2026:24315-1 SUSE-SU-2026:24181-1 SUSE-SU-2026:24182-1

kernel-rt openSUSE Leap 16.0 6.12.0-160000.39.1
dtb-aarch64 openSUSE Leap 16.0 6.12.0-160000.39.1
kernel-64kb openSUSE Leap 16.0 6.12.0-160000.39.1
kernel-syms openSUSE Leap 16.0 6.12.0-160000.39.1
kernel-azure openSUSE Leap 16.0 6.12.0-160000.39.1
kernel-obs-qa openSUSE Leap 16.0 6.12.0-160000.39.1
kernel-source openSUSE Leap 16.0 6.12.0-160000.39.1
kernel-default openSUSE Leap 16.0 6.12.0-160000.39.1

opensuse advisories openSUSE-SU-2026:22091-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-72247 updated 2026-11-06 cvss 5.3

kernel: netfilter: nf_conncount: fix zone comparison in tuple dedup

Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +83 more Red Hat Enterprise Linux 10 kernel
affected: workaround, no fix available “Fix deferred”
Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more
not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation: none
Automatable: yes
Technical impact: partial
Assessed: 23 d ago (2026-10-16)

Exploit prediction

0.70% chance of exploitation in the next 30 days, higher than 53% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CNA	3.1	7.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

Linux Linux

Classification

Technology feeds

Linux kernel rss critical rss

References

Sources

CVE List CVE-2026-72247
NVD CVE-2026-72247

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary