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vuln-cve/data/2026/80xxx/CVE-2026-80634.json
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{
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"cveMetadata": {
"cveId": "CVE-2026-80634",
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"state": "PUBLISHED",
"assignerShortName": "Linux",
"dateReserved": "2026-08-26T14:34:25.777Z",
"datePublished": "2026-08-28T06:48:49.022Z",
"dateUpdated": "2026-10-30T12:30:48.907Z"
},
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"dateUpdated": "2026-10-30T12:30:48.907Z"
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"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: flowtable: avoid num_encaps underflow on bridge VLAN untag\n\nThe DEV_PATH_BR_VLAN_UNTAG case post-decrements info->num_encaps\ninside WARN_ON_ONCE(). num_encaps is u8, so if it's already 0 the\ndecrement still happens and wraps it to 255. The break only leaves\nthe inner switch -- a later path entry can set info->indev back to\na real device, and we end up returning with num_encaps == 255.\n\nnft_dev_forward_path() then walks info.encap[] (size 2) up to\nnum_encaps, which means an OOB stack read and a bogus count copied\ninto the route descriptor.\n\nShould only happen on a malformed bridge path stack, hence the WARN,\nbut worth handling sanely. Move the decrement out of the WARN.\n\n[ While at this, remove the WARN_ON_ONCE since this can only happen\n with a buggy bridge path stack --pablo ]."
}
],
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{
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"version": "3.1",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
"baseScore": 9.8,
"baseSeverity": "CRITICAL"
},
"scenarios": [
{
"lang": "en",
"value": "AV:N - The bug is hit in nft_flow_offload_eval on NF_INET_FORWARD when remotely sourced TCP/UDP packets matching a conntrack flow trigger nft_flow_route() and nft_dev_forward_path() during softirq packet processing on nftables flowtable routers/gateways, not via netlink configuration APIs.\nAC:L - Once an nftables flowtable with bridge VLAN filtering is deployed, an attacker can establish confirmed TCP/UDP flows and steer traffic through the affected bridge/VLAN topology to reach nft_dev_path_info() without races or other conditions outside the attacker's control.\nPR:N - Flowtable and bridge VLAN setup are administrator deployment prerequisites; a remote sender needs no local account, authentication, or CAP_NET_ADMIN on the victim to trigger flow offload path resolution while forwarding traffic through the configured bridge.\nUI:N - Exploitation requires only sending network packets processed automatically on the forwarding path; no victim must open files, mount filesystems, or take any interactive action beyond normal traffic through the router.\nS:U - Out-of-bounds stack reads and writes in nft_dev_forward_path() corrupt kernel stack memory and route descriptors on the affected host only; this is standard kernel compromise within one security authority, not a VM escape or cross-boundary sandbox break.\nC:H - When num_encaps underflows to 255, nft_dev_forward_path() loops up to 255 times over info.encap[2], performing out-of-bounds stack reads of adjacent kernel stack memory that can disclose pointers and other sensitive data.\nI:H - The same loop writes attacker-influenced encap values past route->tuple[].in.encap[2] on the stack, corrupting adjacent route fields and stack data in ways that can be leveraged for arbitrary kernel writes and control-flow hijack.\nA:H - Massive out-of-bounds stack corruption during flow offload setup in softirq context can cause immediate kernel oops/panic and reliable denial of service on forwarding routers processing malicious traffic through vulnerable bridge VLAN paths."
}
]
}
],
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"product": "Linux",
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"defaultStatus": "unaffected",
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"programFiles": [
"net/netfilter/nf_flow_table_path.c"
],
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"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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],
"versions": [
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{
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{
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"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"versionType": "semver"
},
{
"version": "6.18.57",
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
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},
{
"version": "7.1.5",
"lessThanOrEqual": "7.1.*",
"status": "unaffected",
"versionType": "semver"
},
{
"version": "7.2",
"lessThanOrEqual": "*",
"status": "unaffected",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
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"nodes": [
{
"operator": "OR",
"negate": false,
"cpeMatch": [
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"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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"references": [
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"url": "https://git.kernel.org/stable/c/9a4e3a9017ba3da2de187b72ed6545641a0d0a84"
},
{
"url": "https://git.kernel.org/stable/c/1b52aeb40c9f04bf50eeb4ea09142139d163e239"
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{
"url": "https://git.kernel.org/stable/c/ee8440bb000fff4ef8acbfc99652851e9ca0a35b"
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},
{
"url": "https://git.kernel.org/stable/c/e052f920773b73be49eb4d8702a9f85de7464363"
}
],
"title": "netfilter: flowtable: avoid num_encaps underflow on bridge VLAN untag",
"x_generator": {
"engine": "bippy-1.2.0"
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},
"adp": [
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"metrics": [
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"type": "ssvc",
"content": {
"id": "CVE-2026-80634",
"role": "CISA Coordinator",
"options": [
{
"Exploitation": "none"
},
{
"Automatable": "yes"
},
{
"Technical Impact": "total"
}
],
"version": "2.0.3",
"timestamp": "2026-10-16T19:19:08.898847Z"
}
}
}
],
"title": "CISA ADP Vulnrichment",
"providerMetadata": {
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"shortName": "CISA-ADP",
"dateUpdated": "2026-10-16T19:26:31.432Z"
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}