CVE-2026-72250 (GCVE-0-2026-72250)
Vulnerability from cvelistv5
Published
2026-08-15 05:54
Modified
2026-08-17 05:42
Severity ?
VLAI Severity ?
EPSS score ?
Summary
In the Linux kernel, the following vulnerability has been resolved:
netfilter: nf_conntrack_reasm: guard mac_header adjustment after IPv6 defrag
nf_ct_frag6_reasm() slides the packet head forward to drop the IPv6
fragment header and then unconditionally advances skb->mac_header:
skb->mac_header += sizeof(struct frag_hdr);
On the NF_INET_LOCAL_OUT defrag path the skb has no link-layer header
yet, so skb->mac_header is still the "not set" sentinel (u16)~0U. Adding
sizeof(struct frag_hdr) wraps it to a small value (0xffff + 8 == 7),
after which skb_mac_header_was_set() wrongly reports a MAC header is
present and skb_mac_header() points into the headroom.
The reassembler has done this unconditional add since it was introduced;
it was harmless while mac_header was a bare pointer, but wrong once
mac_header became a u16 offset whose unset state is the ~0U sentinel
tested by skb_mac_header_was_set(). The sibling net/ipv6/reassembly.c
does the same relocation and does guard the adjustment; mirror the
guard here.
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Linux | Linux |
Version: 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 Version: 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 Version: 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 Version: 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 Version: 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 Version: 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 Version: 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 Version: 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 |
||
{
"containers": {
"cna": {
"affected": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"net/ipv6/netfilter/nf_conntrack_reasm.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
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"status": "affected",
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"versionType": "git"
},
{
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{
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],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "2.6.15"
},
{
"lessThan": "2.6.15",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.10.*",
"status": "unaffected",
"version": "5.10.261",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.15.*",
"status": "unaffected",
"version": "5.15.212",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.1.*",
"status": "unaffected",
"version": "6.1.178",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"version": "6.6.145",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.97",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"version": "6.18.40",
"versionType": "semver"
},
{
"lessThanOrEqual": "7.1.*",
"status": "unaffected",
"version": "7.1.5",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.2",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
{
"nodes": [
{
"cpeMatch": [
{
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"versionEndExcluding": "5.10.261",
"versionStartIncluding": "2.6.15",
"vulnerable": true
},
{
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},
{
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},
{
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},
{
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},
{
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"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
]
}
],
"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-\u003emac_header:\n\n\tskb-\u003emac_header += sizeof(struct frag_hdr);\n\nOn the NF_INET_LOCAL_OUT defrag path the skb has no link-layer header\nyet, so skb-\u003emac_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": {
"baseScore": 7.8,
"baseSeverity": "HIGH",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
},
"scenarios": [
{
"lang": "en",
"value": "AV:L - The bug triggers only when nf_ct_frag6_reasm() runs on NF_INET_LOCAL_OUT with skb-\u003emac_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": {
"dateUpdated": "2026-08-17T05:42:02.183Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"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"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2026-72250",
"datePublished": "2026-08-15T05:54:39.134Z",
"dateReserved": "2026-08-09T03:40:39.915Z",
"dateUpdated": "2026-08-17T05:42:02.183Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.
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