CVE-2026-72247: Linux kernel · netfilter: nf_conncount: fix zone comparison in tuple dedup
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 7.5 High · fixed in 5.15.0-1117.124~20.04.1 : patch Linux kernel soon.
Data as of 28 Oct 2026, 00:58 UTC
- Patch
- Available – fixed in 5.15.0-1117.124~20.04.1, 5.15.0-1123.132~20.04.1, 5.15.0-1122.131~20.04.1 +56
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:HExploitation evidence
Disclosed: evidence found.
CVE published 15 Aug 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
Upgrade to a fixed release listed under Affected software.
Patches and advisories
- ubuntu.com/security/notices/USN-8876-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8878-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8879-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8877-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8875-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8888-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8889-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8887-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8886-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8888-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8887-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8875-2 (opens in a new tab)
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Ubuntu 26.04 LTSlinuxpkg:deb/ubuntu/linux?arch=source&distro=resoluteOther threats | Affected
| Fixed in
|
Ubuntu 26.04 LTSlinux-awspkg:deb/ubuntu/linux-aws?arch=source&distro=resoluteOther threats | Affected
| Fixed in
|
Ubuntu 26.04 LTSlinux-azurepkg:deb/ubuntu/linux-azure?arch=source&distro=resoluteOther threats | Affected
| Fixed in
|
Ubuntu 26.04 LTSlinux-azure-fdepkg:deb/ubuntu/linux-azure-fde?arch=source&distro=resoluteOther threats | Affected
| Fixed in
|
Ubuntu 26.04 LTSlinux-gcppkg:deb/ubuntu/linux-gcp?arch=source&distro=resoluteOther threats | Affected
| Fixed in
|
Ubuntu 26.04 LTSlinux-gkepkg:deb/ubuntu/linux-gke?arch=source&distro=resoluteOther threats | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
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.
References
- ubuntu.com/security/CVE-2026-72247 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-72247 (opens in a new tab)
- git.kernel.org/linus/f62c41b4910e65da396ec9a8c40c1fe7fe82e449 (opens in a new tab)
- git.kernel.org/stable/c/35a56e2a46b90e6bd4ca816b80e9cb8d20dfc3ce (opens in a new tab)
- git.kernel.org/stable/c/3cd9a5792cbea81139c24320986dd0db69e9b5d0 (opens in a new tab)
- git.kernel.org/stable/c/4f30a89c0ed2418719a1144881c2635b940b543d (opens in a new tab)
- git.kernel.org/stable/c/6ff07ac5405bea4d4ead3559fc123f987576424a (opens in a new tab)
- git.kernel.org/stable/c/78b5d6dbc860776161f9e9206b06ff8a01f531ab (opens in a new tab)
- git.kernel.org/stable/c/7bdc3c0985ecf17b957811fedcc684acdf698acc (opens in a new tab)
- git.kernel.org/stable/c/82fc35e0da9a91db9a034f8311f18f77a599ae3f (opens in a new tab)
- git.kernel.org/stable/c/f62c41b4910e65da396ec9a8c40c1fe7fe82e449 (opens in a new tab)
- ubuntu.com/security/notices/USN-8876-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8878-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8879-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8877-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8875-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8888-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8889-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8887-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8886-1 (opens in a new tab)