What’s Vulnerable › Vulnerabilities

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

• Severity: unknown
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-08-15 · updated 2026-08-17

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.

Affected products

• Linux kernel: 2.6.30 — fixed in 7.2

How to fix

Upgrade to a fixed version: Linux kernel 7.2. Check the vendor advisory for mitigations.

References

• https://git.kernel.org/stable/c/07f9ddbf5e799c24a3a52ec9bd7b729a6f6d69d5
• https://git.kernel.org/stable/c/13ea4f86cf738c74be2146886ac261988a631e62
• https://git.kernel.org/stable/c/4558bd7b47c7be82dffd837f27be8ea3ecee557d
• https://git.kernel.org/stable/c/4cb8b5f586e41c187942291cc0938006077fa79e
• https://git.kernel.org/stable/c/5b2d4f0010018a7aa3495aa1dbf1b7a34011e7aa
• https://git.kernel.org/stable/c/5feba91006ec92da57acc1cc2e34df623b98541e
• https://git.kernel.org/stable/c/d5f9d050b0b267227c1f02f11021872c7768a9cc
• https://git.kernel.org/stable/c/fac2fdac3baad9ffd12b3b0bba4374d4b3585d54

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