VulnerabilityPublished 15 Aug 2026Updated 6 Nov 2026

CVE-2026-72256: Linux kernel · netfilter: xt_cluster: reject template conntracks in hash match

Affects Linux kernelSource CVE Database V5

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Not known to be exploited · fixed in fac2fdac3baad9ffd12b3b0bba4374d4b3585d54 : update Linux kernel when convenient.

Data as of 6 Nov 2026, 17:04 UTC

Severity

Unrated

Rated by Threat Radar · CVSS not yet scored by NVD

Thin evidence

One scorer or none

Exploitation: No evidence of active exploitation and no public proof of concept
Automatable: Attackers cannot reliably automate steps 1–4 of the kill chain
Technical impact: Limited control over the software or limited information exposure

CISA SSVC assessment, 2026-11-06.

Patch

Available – fixed in fac2fdac3baad9ffd12b3b0bba4374d4b3585d54, d5f9d050b0b267227c1f02f11021872c7768a9cc, 4558bd7b47c7be82dffd837f27be8ea3ecee557d +5

Exploitation evidence

Disclosed: evidence found.
CVE published 15 Aug 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: 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 6 Nov 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ 0269ea4937343536ec7e85649932bc8c9686ea78, < fac2fdac3baad9ffd12b3b0bba4374d4b3585d54	Fixed in fac2fdac3baad9ffd12b3b0bba4374d4b3585d54
LinuxLinux	Affected ≥ 0269ea4937343536ec7e85649932bc8c9686ea78, < d5f9d050b0b267227c1f02f11021872c7768a9cc	Fixed in d5f9d050b0b267227c1f02f11021872c7768a9cc
LinuxLinux	Affected ≥ 0269ea4937343536ec7e85649932bc8c9686ea78, < 4558bd7b47c7be82dffd837f27be8ea3ecee557d	Fixed in 4558bd7b47c7be82dffd837f27be8ea3ecee557d
LinuxLinux	Affected ≥ 0269ea4937343536ec7e85649932bc8c9686ea78, < 13ea4f86cf738c74be2146886ac261988a631e62	Fixed in 13ea4f86cf738c74be2146886ac261988a631e62
LinuxLinux	Affected ≥ 0269ea4937343536ec7e85649932bc8c9686ea78, < 07f9ddbf5e799c24a3a52ec9bd7b729a6f6d69d5	Fixed in 07f9ddbf5e799c24a3a52ec9bd7b729a6f6d69d5
LinuxLinux	Affected ≥ 0269ea4937343536ec7e85649932bc8c9686ea78, < 5feba91006ec92da57acc1cc2e34df623b98541e	Fixed in 5feba91006ec92da57acc1cc2e34df623b98541e

Description

In the Linux kernel, the following vulnerability has been resolved: netfilter: xt_cluster: reject template conntracks in hash match xt_cluster_mt() treats any non-NULL nf_ct_get() result as a fully initialized conntrack and passes it to xt_cluster_hash(). This causes a state confusion bug when the raw table CT target attaches a template conntrack to skb->_nfct before normal conntrack processing. Templates carry IPS_TEMPLATE status but do not have a valid tuple for hashing yet, so xt_cluster_hash() can hit its WARN_ON() path on the zeroed l3num field. Reject template conntracks before hashing them. This matches existing netfilter handling for template objects and avoids hashing incomplete conntrack state.

References

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