Vulnerability in Linux kernel (CVE-2026-72251)
Summary
Vulnerability in Linux kernel (CVE-2026-72251). Successful exploitation can lead to full system takeover.
Original description
The description as published by the source.
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: NIST National Vulnerability Database NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-72251 has been found in Linux kernel.
Successful exploitation can lead to full system takeover. CVSS score: 9.8/10.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "Linux kernel CVE-2026-72251" on the vendor's site.
CVE-2026-72251 (Linux kernel) — CVSS v3 9.8
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (unclassified) exists in Linux kernel.
Check the vendor advisory for the affected versions of Linux kernel.
Severity: Critical (CVSS 9.8/10). Successful exploitation can lead to full system takeover.
Update to the patched release per vendor advisory.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Audit SBOM/dependencies to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
Audit SBOM/dependencies for affected components.資産台帳・SBOM・依存マニフェストで Linux kernel を使っているサービスとバージョンを洗い出す。
-
2Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
Fix status by distribution
Fixed packages published by each distribution for this CVE
- BellSoft Alpaquita BELL-CVE-2026-72251 linux-lts Fixed in: 6.1.182-r0
- Debian DEBIAN-CVE-2026-72251 linux Fixed in: 6.1.180-1
- Ubuntu UBUNTU-CVE-2026-72251 linux
References
- advisory nvd.nist.gov
- advisory github.com
- package git.kernel.org
- web git.kernel.org
- web git.kernel.org
- web git.kernel.org
- web git.kernel.org
- web git.kernel.org
- web git.kernel.org
- web git.kernel.org
- web git.kernel.org
- web github.com