CVE-2026-74743 (GCVE-0-2026-74743)
Vulnerability from cvelistv5
Published
2026-08-26 14:36
Modified
2026-08-27 05:01
Severity ?
VLAI Severity ?
EPSS score ?
Summary
In the Linux kernel, the following vulnerability has been resolved:
macvlan: inherit needed_headroom and needed_tailroom from lowerdev
macvlan devices inherit hard_header_len from lowerdev during macvlan_init(),
but leave needed_headroom and needed_tailroom set to 0.
When the underlying lowerdev requires extra headroom or tailroom for
headers/trailers (e.g. macsec, ipsec, wireguard, tunnels, or veth with rx
headroom), upper layers calculating packet headroom and tailroom fail to
reserve sufficient space.
This can result in reallocation overhead, skb headroom underflows, or KASAN
slab-use-after-free crashes when dev_hard_header() / macvlan_hard_header()
prepends header data or when lower devices append tailroom.
Fix this by:
1. Inheriting needed_headroom and needed_tailroom from lowerdev in macvlan_init().
2. Propagating needed_headroom and needed_tailroom updates to attached macvlans
in macvlan_device_event() when receiving NETDEV_FEAT_CHANGE events.
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Linux | Linux |
Version: b863ceb7ddcea8c55fcf1d7b2ac591d50aa7ed53 Version: b863ceb7ddcea8c55fcf1d7b2ac591d50aa7ed53 Version: b863ceb7ddcea8c55fcf1d7b2ac591d50aa7ed53 Version: b863ceb7ddcea8c55fcf1d7b2ac591d50aa7ed53 Version: b863ceb7ddcea8c55fcf1d7b2ac591d50aa7ed53 Version: b863ceb7ddcea8c55fcf1d7b2ac591d50aa7ed53 |
||
{
"containers": {
"cna": {
"affected": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"drivers/net/macvlan.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"lessThan": "8cd90e850e434577bf6774778657d26d6995e53f",
"status": "affected",
"version": "b863ceb7ddcea8c55fcf1d7b2ac591d50aa7ed53",
"versionType": "git"
},
{
"lessThan": "28afc87bd8da0b3348bbbd834c8a89e83712cf5e",
"status": "affected",
"version": "b863ceb7ddcea8c55fcf1d7b2ac591d50aa7ed53",
"versionType": "git"
},
{
"lessThan": "8f6a05dbac05725e0786701eb04778c5bdbe4eaa",
"status": "affected",
"version": "b863ceb7ddcea8c55fcf1d7b2ac591d50aa7ed53",
"versionType": "git"
},
{
"lessThan": "96fa90b74385b7f2b0d97251dd43d5ee6ca44668",
"status": "affected",
"version": "b863ceb7ddcea8c55fcf1d7b2ac591d50aa7ed53",
"versionType": "git"
},
{
"lessThan": "bc9a00fb78e32bccc39d763bfd13a450705bac5d",
"status": "affected",
"version": "b863ceb7ddcea8c55fcf1d7b2ac591d50aa7ed53",
"versionType": "git"
},
{
"lessThan": "cef51860becd9700217c81732ca1eb1ea6ed6fe1",
"status": "affected",
"version": "b863ceb7ddcea8c55fcf1d7b2ac591d50aa7ed53",
"versionType": "git"
}
]
},
{
"defaultStatus": "affected",
"product": "Linux",
"programFiles": [
"drivers/net/macvlan.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "2.6.23"
},
{
"lessThan": "2.6.23",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.1.*",
"status": "unaffected",
"version": "6.1.184",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"version": "6.6.153",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.105",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"version": "6.18.46",
"versionType": "semver"
},
{
"lessThanOrEqual": "7.1.*",
"status": "unaffected",
"version": "7.1.10",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.2",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.1.184",
"versionStartIncluding": "2.6.23",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.6.153",
"versionStartIncluding": "2.6.23",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.12.105",
"versionStartIncluding": "2.6.23",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.18.46",
"versionStartIncluding": "2.6.23",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "7.1.10",
"versionStartIncluding": "2.6.23",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "7.2",
"versionStartIncluding": "2.6.23",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmacvlan: inherit needed_headroom and needed_tailroom from lowerdev\n\nmacvlan devices inherit hard_header_len from lowerdev during macvlan_init(),\nbut leave needed_headroom and needed_tailroom set to 0.\n\nWhen the underlying lowerdev requires extra headroom or tailroom for\nheaders/trailers (e.g. macsec, ipsec, wireguard, tunnels, or veth with rx\nheadroom), upper layers calculating packet headroom and tailroom fail to\nreserve sufficient space.\n\nThis can result in reallocation overhead, skb headroom underflows, or KASAN\nslab-use-after-free crashes when dev_hard_header() / macvlan_hard_header()\nprepends header data or when lower devices append tailroom.\n\nFix this by:\n1. Inheriting needed_headroom and needed_tailroom from lowerdev in macvlan_init().\n2. Propagating needed_headroom and needed_tailroom updates to attached macvlans\n in macvlan_device_event() when receiving NETDEV_FEAT_CHANGE events."
}
],
"metrics": [
{
"cvssV3_1": {
"baseScore": 9.8,
"baseSeverity": "CRITICAL",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
},
"scenarios": [
{
"lang": "en",
"value": "AV:N - The bug fires on the macvlan transmit path (ip_finish_output2/neigh_resolve_output/macvlan_hard_header) when kernel-generated replies or forwarded traffic egress a macvlan netdev; remote peers trigger this by sending TCP/UDP/ICMP to an address on a pre-configured macvlan interface.\nAC:L - Once macvlan is stacked on a lowerdev with nonzero needed_headroom (WireGuard, MACsec, IPsec, tunnels, veth RX headroom), ordinary packets reliably hit under-reserved skb headroom/tailroom during dev_hard_header() without races or uncontrollable timing.\nPR:N - A remote attacker needs no local account or capabilities; sending routable traffic to a macvlan address suffices. Administrative macvlan setup is environmental (like other netdev CVEs), not an attacker privilege requirement.\nUI:N - Exploitation requires only normal network delivery to a reachable macvlan address; no victim must open files, mount filesystems, or perform any interactive action beyond existing connectivity.\nS:U - Impact is kernel skb heap corruption, slab-use-after-free, or panic within the host network stack; it does not cross VM, IOMMU, or container security boundaries into a separate authority.\nC:H - The fix commit documents KASAN slab-use-after-free from skb headroom underflow during header prepending; this class of kernel heap corruption is exploitable for arbitrary memory disclosure beyond a bounded leak.\nI:H - Insufficient headroom causes skb_push underflows and slab UAF during pskb_expand_head/reallocation, providing kernel heap write primitives that can be leveraged for control-flow hijacking and privilege escalation.\nA:H - The failure mode includes skb_under_panic (kernel BUG/panic) and KASAN-detected slab UAF crashes, causing immediate host kernel denial of service on affected transmit paths."
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-08-27T05:01:04.222Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/8cd90e850e434577bf6774778657d26d6995e53f"
},
{
"url": "https://git.kernel.org/stable/c/28afc87bd8da0b3348bbbd834c8a89e83712cf5e"
},
{
"url": "https://git.kernel.org/stable/c/8f6a05dbac05725e0786701eb04778c5bdbe4eaa"
},
{
"url": "https://git.kernel.org/stable/c/96fa90b74385b7f2b0d97251dd43d5ee6ca44668"
},
{
"url": "https://git.kernel.org/stable/c/bc9a00fb78e32bccc39d763bfd13a450705bac5d"
},
{
"url": "https://git.kernel.org/stable/c/cef51860becd9700217c81732ca1eb1ea6ed6fe1"
}
],
"title": "macvlan: inherit needed_headroom and needed_tailroom from lowerdev",
"x_generator": {
"engine": "bippy-1.2.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2026-74743",
"datePublished": "2026-08-26T14:36:54.175Z",
"dateReserved": "2026-08-15T05:44:03.930Z",
"dateUpdated": "2026-08-27T05:01:04.222Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
Loading…
Loading…
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.
Loading…
Loading…