{"id":"CVE-2026-72250","state":"PUBLISHED","title":"netfilter: nf_conntrack_reasm: guard mac_header adjustment after IPv6 defrag","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: nf_conntrack_reasm: guard mac_header adjustment after IPv6 defrag\n\nnf_ct_frag6_reasm() slides the packet head forward to drop the IPv6\nfragment header and then unconditionally advances skb->mac_header:\n\n\tskb->mac_header += sizeof(struct frag_hdr);\n\nOn the NF_INET_LOCAL_OUT defrag path the skb has no link-layer header\nyet, so skb->mac_header is still the \"not set\" sentinel (u16)~0U. Adding\nsizeof(struct frag_hdr) wraps it to a small value (0xffff + 8 == 7),\nafter which skb_mac_header_was_set() wrongly reports a MAC header is\npresent and skb_mac_header() points into the headroom.\n\nThe reassembler has done this unconditional add since it was introduced;\nit was harmless while mac_header was a bare pointer, but wrong once\nmac_header became a u16 offset whose unset state is the ~0U sentinel\ntested by skb_mac_header_was_set(). The sibling net/ipv6/reassembly.c\ndoes the same relocation and does guard the adjustment; mirror the\nguard here.","publishedAt":"2026-08-15T05:54:39.134Z","updatedAt":"2026-10-16T18:55:13.023Z","severity":{"score":7.8,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1","status":"affected","lessThan":"6e8cd710ca35c576f5f2e5a396047c9ac61f75e5","versionType":"git"},{"version":"9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1","status":"affected","lessThan":"2a95ec21824a8ad81ad660b12231456fc0ac9830","versionType":"git"},{"version":"9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1","status":"affected","lessThan":"bbcdef2061b170af45702ce6b359c02c12acfc94","versionType":"git"},{"version":"9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1","status":"affected","lessThan":"cd0d7bbc027b4d3329712cdcdeb4e5567ffd0d58","versionType":"git"},{"version":"9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1","status":"affected","lessThan":"53ef70a315420ed31581d38343684b3bf9a3c76d","versionType":"git"},{"version":"9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1","status":"affected","lessThan":"a58230f3a7c4f6c3261786bc1efb72c42e68cd25","versionType":"git"},{"version":"9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1","status":"affected","lessThan":"00bdce2fda7e430d24cfbc96764a1b96deb31f82","versionType":"git"},{"version":"9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1","status":"affected","lessThan":"3b08fed5b7e0d5e3a25d73ef3ba09cd33ade16c9","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv6/netfilter/nf_conntrack_reasm.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"2.6.15","status":"affected"},{"version":"0","status":"unaffected","lessThan":"2.6.15","versionType":"semver"},{"version":"5.10.261","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.212","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.178","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.145","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.97","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.40","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.5","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv6/netfilter/nf_conntrack_reasm.c"]}],"references":["https://git.kernel.org/stable/c/6e8cd710ca35c576f5f2e5a396047c9ac61f75e5","https://git.kernel.org/stable/c/2a95ec21824a8ad81ad660b12231456fc0ac9830","https://git.kernel.org/stable/c/bbcdef2061b170af45702ce6b359c02c12acfc94","https://git.kernel.org/stable/c/cd0d7bbc027b4d3329712cdcdeb4e5567ffd0d58","https://git.kernel.org/stable/c/53ef70a315420ed31581d38343684b3bf9a3c76d","https://git.kernel.org/stable/c/a58230f3a7c4f6c3261786bc1efb72c42e68cd25","https://git.kernel.org/stable/c/00bdce2fda7e430d24cfbc96764a1b96deb31f82","https://git.kernel.org/stable/c/3b08fed5b7e0d5e3a25d73ef3ba09cd33ade16c9"],"weaknesses":[],"ingestedAt":"2026-10-29T20:12:58.252Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/72xxx/CVE-2026-72250.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-72250","state":"PUBLISHED","datePublished":"2026-08-15T05:54:39.134Z","dateUpdated":"2026-10-16T18:55:13.023Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-08-09T03:40:39.915Z"},"containers":{"cna":{"title":"netfilter: nf_conntrack_reasm: guard mac_header adjustment after IPv6 defrag","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: nf_conntrack_reasm: guard mac_header adjustment after IPv6 defrag\n\nnf_ct_frag6_reasm() slides the packet head forward to drop the IPv6\nfragment header and then unconditionally advances skb->mac_header:\n\n\tskb->mac_header += sizeof(struct frag_hdr);\n\nOn the NF_INET_LOCAL_OUT defrag path the skb has no link-layer header\nyet, so skb->mac_header is still the \"not set\" sentinel (u16)~0U. Adding\nsizeof(struct frag_hdr) wraps it to a small value (0xffff + 8 == 7),\nafter which skb_mac_header_was_set() wrongly reports a MAC header is\npresent and skb_mac_header() points into the headroom.\n\nThe reassembler has done this unconditional add since it was introduced;\nit was harmless while mac_header was a bare pointer, but wrong once\nmac_header became a u16 offset whose unset state is the ~0U sentinel\ntested by skb_mac_header_was_set(). The sibling net/ipv6/reassembly.c\ndoes the same relocation and does guard the adjustment; mirror the\nguard here."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1","status":"affected","lessThan":"6e8cd710ca35c576f5f2e5a396047c9ac61f75e5","versionType":"git"},{"version":"9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1","status":"affected","lessThan":"2a95ec21824a8ad81ad660b12231456fc0ac9830","versionType":"git"},{"version":"9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1","status":"affected","lessThan":"bbcdef2061b170af45702ce6b359c02c12acfc94","versionType":"git"},{"version":"9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1","status":"affected","lessThan":"cd0d7bbc027b4d3329712cdcdeb4e5567ffd0d58","versionType":"git"},{"version":"9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1","status":"affected","lessThan":"53ef70a315420ed31581d38343684b3bf9a3c76d","versionType":"git"},{"version":"9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1","status":"affected","lessThan":"a58230f3a7c4f6c3261786bc1efb72c42e68cd25","versionType":"git"},{"version":"9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1","status":"affected","lessThan":"00bdce2fda7e430d24cfbc96764a1b96deb31f82","versionType":"git"},{"version":"9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1","status":"affected","lessThan":"3b08fed5b7e0d5e3a25d73ef3ba09cd33ade16c9","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv6/netfilter/nf_conntrack_reasm.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"2.6.15","status":"affected"},{"version":"0","status":"unaffected","lessThan":"2.6.15","versionType":"semver"},{"version":"5.10.261","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.212","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.178","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.145","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.97","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.40","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.5","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv6/netfilter/nf_conntrack_reasm.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/6e8cd710ca35c576f5f2e5a396047c9ac61f75e5"},{"url":"https://git.kernel.org/stable/c/2a95ec21824a8ad81ad660b12231456fc0ac9830"},{"url":"https://git.kernel.org/stable/c/bbcdef2061b170af45702ce6b359c02c12acfc94"},{"url":"https://git.kernel.org/stable/c/cd0d7bbc027b4d3329712cdcdeb4e5567ffd0d58"},{"url":"https://git.kernel.org/stable/c/53ef70a315420ed31581d38343684b3bf9a3c76d"},{"url":"https://git.kernel.org/stable/c/a58230f3a7c4f6c3261786bc1efb72c42e68cd25"},{"url":"https://git.kernel.org/stable/c/00bdce2fda7e430d24cfbc96764a1b96deb31f82"},{"url":"https://git.kernel.org/stable/c/3b08fed5b7e0d5e3a25d73ef3ba09cd33ade16c9"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.8,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:L - The bug triggers only when nf_ct_frag6_reasm() runs on NF_INET_LOCAL_OUT with skb->mac_header still unset (~0U). That requires injecting pre-fragmented IPv6 into the local output path (e.g., AF_INET6 SOCK_RAW), not standard remotely received PRE_ROUTING traffic where mac_header is already valid and the adjustment is correct.\nAC:L - An attacker who can send raw IPv6 fragments can reliably complete conntrack reassembly by crafting matching fragment ID/source/destination tuples. nf_defrag_ipv6 is enabled automatically whenever IPv6 connection tracking is in use (typical on nftables/iptables hosts), so no rare race or admin-only timing is needed.\nPR:L - Triggering handcrafted IPv6 fragments requires CAP_NET_RAW. On systems with unprivileged user namespaces, a local user can obtain CAP_NET_RAW (and CAP_NET_ADMIN for conntrack) via unshare -Urn, so required privileges are Low rather than High root-only access.\nUI:N - Exploitation requires only attacker-controlled fragmented IPv6 traffic and an active conntrack defrag path; it does not depend on any victim user action such as opening files, mounting filesystems, or clicking links.\nS:U - Impact is skb metadata corruption within the kernel network stack in the same security domain. It does not inherently cross VM, container runtime, or IOMMU boundaries without separate privilege-escalation exploitation.\nC:H - Adding sizeof(frag_hdr) to the unset mac_header sentinel wraps to a small offset, so skb_mac_header_was_set() becomes true and skb_mac_header() points into skb headroom. Downstream netfilter/nft L2 helpers can then perform out-of-bounds reads, leaking stale kernel data from headroom.\nI:H - The bogus mac_header and inflated skb_mac_header_len() misdirect later L2 header access and nft payload/meta write paths to incorrect offsets in skb headroom or packet data, enabling memory corruption that can be leveraged for arbitrary kernel writes or control-flow hijacking.\nA:H - Corrupted skb header state can cause kernel oops, panic, or fatal faults when subsequent LOCAL_OUT, netfilter, or output routines use the invalid MAC header pointer, and the associated memory corruption can crash the system even without full exploit development."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-17T05:42:02.183Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.15","versionEndExcluding":"5.10.261"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.15","versionEndExcluding":"5.15.212"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.15","versionEndExcluding":"6.1.178"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.15","versionEndExcluding":"6.6.145"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.15","versionEndExcluding":"6.12.97"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.15","versionEndExcluding":"6.18.40"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.15","versionEndExcluding":"7.1.5"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.15","versionEndExcluding":"7.2"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2026-72250","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"total"}],"version":"2.0.3","timestamp":"2026-10-16T18:45:08.646891Z"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-16T18:55:13.023Z"}}]}}}