{"apiVersion":"1.0","identifier":"CVE-2026-72251","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. ------------------------------------------------------------------------ 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.","publishedAt":"2026-08-15T06:21:52","lastModifiedAt":"2026-08-17T06:18:27","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-72251","cvssScore":9.8,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","epssProbability":0.00714,"riskScore":1.04,"affectedProduct":"Linux kernel","affectedVersions":"unknown","vulnerabilityType":"Kernel","operatingSystems":[],"links":{"self":"https://www.redsauce.net/api/cves/CVE-2026-72251","webPages":{"es":"https://www.redsauce.net/es/cves/CVE-2026-72251","en":"https://www.redsauce.net/en/cves/CVE-2026-72251","fr":"https://www.redsauce.net/fr/cves/CVE-2026-72251","pt":"https://www.redsauce.net/pt/cves/CVE-2026-72251","de":"https://www.redsauce.net/de/cves/CVE-2026-72251","sk":"https://www.redsauce.net/sk/cves/CVE-2026-72251","el":"https://www.redsauce.net/el/cves/CVE-2026-72251"},"source":"https://nvd.nist.gov/vuln/detail/CVE-2026-72251"}}