{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-72250", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-08-09T03:40:39.915Z", "datePublished": "2026-08-15T05:54:39.134Z", "dateUpdated": "2026-08-17T05:42:02.183Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-17T05:42:02.183Z" }, "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." } ], "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." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/ipv6/netfilter/nf_conntrack_reasm.c" ], "versions": [ { "version": "9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1", "lessThan": "6e8cd710ca35c576f5f2e5a396047c9ac61f75e5", "status": "affected", "versionType": "git" }, { "version": "9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1", "lessThan": "2a95ec21824a8ad81ad660b12231456fc0ac9830", "status": "affected", "versionType": "git" }, { "version": "9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1", "lessThan": "bbcdef2061b170af45702ce6b359c02c12acfc94", "status": "affected", "versionType": "git" }, { "version": "9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1", "lessThan": "cd0d7bbc027b4d3329712cdcdeb4e5567ffd0d58", "status": "affected", "versionType": "git" }, { "version": "9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1", "lessThan": "53ef70a315420ed31581d38343684b3bf9a3c76d", "status": "affected", "versionType": "git" }, { "version": "9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1", "lessThan": "a58230f3a7c4f6c3261786bc1efb72c42e68cd25", "status": "affected", "versionType": "git" }, { "version": "9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1", "lessThan": "00bdce2fda7e430d24cfbc96764a1b96deb31f82", "status": "affected", "versionType": "git" }, { "version": "9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1", "lessThan": "3b08fed5b7e0d5e3a25d73ef3ba09cd33ade16c9", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/ipv6/netfilter/nf_conntrack_reasm.c" ], "versions": [ { "version": "2.6.15", "status": "affected" }, { "version": "0", "lessThan": "2.6.15", "status": "unaffected", "versionType": "semver" }, { "version": "5.10.261", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.15.212", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.1.178", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.145", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.97", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.40", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.1.5", "lessThanOrEqual": "7.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "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" } ] } ] } ], "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" } ], "title": "netfilter: nf_conntrack_reasm: guard mac_header adjustment after IPv6 defrag", "x_generator": { "engine": "bippy-1.2.0" } } } }