netfilter: xt_cluster: reject template conntracks in hash match
Key facts
- Attack vector
- —
- Privileges required
- —
- User interaction
- —
- Attack complexity
- —
- Impact type
- —
- Confidentiality · integrity · availability
- —
- Fix status
- Partial Red Hat: 5 without a fix
No CVSS vector from any source. Fix status from CNA and Red Hat.
Summary
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.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| Linux | Linux | 2.6.30 and later | 5.10.261, 5.15.212, 6.1.178, 6.6.145, 6.12.97, 6.18.40, 7.1.5, 7.2 | Patch available | CNA |
- Linux VendorLinux Affected 2.6.30 and later Fixed in 5.10.261, 5.15.212, 6.1.178, 6.6.145, 6.12.97, 6.18.40, 7.1.5, 7.2 Patch available CNA
Remediation
- Fix · CNA Linux (Linux) Fixed in 5.10.261, 5.15.212, 6.1.178, 6.6.145, 6.12.97, 6.18.40, 7.1.5, 7.2
Vendor assessments
Red Hat
Red Hat rating: Moderate. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat Enterprise Linux 10 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 6 | Affected | No fix planned: Out of support scope |
| Red Hat Enterprise Linux 7 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 8 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 9 | Affected | No fix yet: Fix deferred |
Timeline
- 2026-10-02 Threatist record created from CVE-2026-72256
- 2026-10-03 Alias added: GHSA-hh4g-5q85-w496
- 2026-11-06 CISA SSVC decision points changed
References
Other 8
- https://git.kernel.org/stable/c/4558bd7b47c7be82dffd837f27be8ea3ecee557d
- https://git.kernel.org/stable/c/d5f9d050b0b267227c1f02f11021872c7768a9cc
- https://git.kernel.org/stable/c/4cb8b5f586e41c187942291cc0938006077fa79e
- https://git.kernel.org/stable/c/fac2fdac3baad9ffd12b3b0bba4374d4b3585d54
- https://git.kernel.org/stable/c/13ea4f86cf738c74be2146886ac261988a631e62
- https://git.kernel.org/stable/c/07f9ddbf5e799c24a3a52ec9bd7b729a6f6d69d5
- https://git.kernel.org/stable/c/5b2d4f0010018a7aa3495aa1dbf1b7a34011e7aa
- https://git.kernel.org/stable/c/5feba91006ec92da57acc1cc2e34df623b98541e
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Sources
- CVE-2026-72256 · CVE Program
- CVE-2026-72256 · NVD
- FIRST EPSS
- GHSA-hh4g-5q85-w496 · GitHub Advisory Database · CC BY 4.0
- CVE-2026-72256 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences