CVE-2026-72251

Technical Description

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.

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Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References