CVE intelligence

CVE-2026-72251

Vulnerability intelligence

Published Aug 15, 2026Sources checked Nov 10, 2026

9.8CRITICALCVSS out of 10

What this means

Review the available evidence

CVE-2026-72251 and is rated Critical severity with a CVSS score of 9.8. It is not in the current CISA KEV record we collected. That does not prove exploitation has not occurred.

What to do next

Remediation and response

Ubuntu Security Notices guidance

Vendor revision: Oct 2, 2026

Vendor remediation details

This update corrects flaws in the following subsystems: - ARM64 architecture; - S390 architecture; - x86 architecture; - DRBD Distributed Replicated Block Device drivers; - InfiniBand drivers; - IOMMU subsystem; - Multiple devices driver; - Network drivers; - Microsoft Azure Network Adapter (MANA) driver; - NVME drivers; - TCM subsystem; - Virtio Host (VHOST) subsystem; - Xen hypervisor drivers; - AFS file system; - File systems infrastructure; - Network file systems library; - Network file system (NFS) client; - NTFS3 file system; - OCFS2 file system; - OrangeFS file system; - SMB network file system; - IPv4 networking; - Sun RPC protocol; - IPv6 networking; - IP tunnels definitions; - Netfilter; - TCP network protocol; - Locking primitives; - 9P file system network protocol; - B.A.T.M.A.

Ubuntu Security Notices guidance

Vendor revision: Sep 30, 2026

Vendor remediation details

Ubuntu Security Notices guidance

Vendor revision: Sep 29, 2026

Vendor remediation details

CISA KEVNot listedBased on the latest collected catalog

EPSS0.7%Estimated 30-day exploitation probability

Ransomware useNot markedCISA KEV ransomware field

Threat actors0Source-linked actor relationships

Overview

What is CVE-2026-72251?

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

netfilter: nf_nat_sip: reload possible stale data pointer

quoting sashiko: ------------------------------------------------------------------------ [..] noticed a potential memory bug and header corruption involving the SIP NAT helper.

In net/netfilter/nf_nat_sip.c:nf_nat_sip(): if (skb_ensure_writable(skb, skb->len)) { nf_ct_helper_log(skb, ct, "cannot mangle packet"); return NF_DROP; } uh = (void *)skb->data + protoff; uh->dest = ct_sip_info->forced_dport; if (!nf_nat_mangle_udp_packet(skb, ct, ctinfo, protoff, 0, 0, NULL, 0)) {

If a cloned or fragmented SKB is reallocated by skb_ensure_writable(), the old data buffer is freed. However, nf_nat_sip() fails to update *dptr to point to the new buffer.

It also appears to use nf_nat_mangle_udp_packet() on what could be a TCP packet, which would overwrite the sequence number with a checksum update. ------------------------------------------------------------------------

nf_conntrack_sip linerizes skbs, hence no fragmented skb can be seen. But clones are possible, so rebuild dptr.

Disable nf_nat_mangle_udp_packet() branch for TCP streams. It doesn't look like this can ever happen, else we should have received bug reports about this, so just check the conntrack is UDP and drop otherwise.

The calling conntrack_sip set ->forced_dport for SIP_HDR_VIA_UDP messages, so I don't think this is ever expected to be true for a TCP stream.

Source: NVD