CVE-2026-72254 (GCVE-0-2026-72254)
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: nft_fib: reject fib expression on the netdev egress hook
A fib expression in a netdev egress base chain dereferences nft_in(pkt),
NULL on the transmit path, causing a NULL pointer dereference at eval.
nft_fib_validate() masks the hook with NF_INET_* values, but netdev hook
numbers are a separate enum that aliases them (NF_NETDEV_EGRESS ==
NF_INET_LOCAL_IN), so an egress chain passes validation and then faults.
Add nft_fib_netdev_validate() that limits each result/flag to the netdev
hook where the device it reads exists: the input-device cases (OIF,
OIFNAME, ADDRTYPE with F_IIF) to ingress, the output-device case (ADDRTYPE
with F_OIF) to egress, ADDRTYPE with no device flag to both. Also restrict
nft_fib_validate() to NFPROTO_IPV4/IPV6/INET so its NF_INET_* masks are
not applied to another family's hooks.
References
Impacted products
{
"containers": {
"cna": {
"affected": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"net/netfilter/nft_fib.c",
"net/netfilter/nft_fib_netdev.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"lessThan": "4fee43759b489559a491f7c95f9bfa7a1d0c7a10",
"status": "affected",
"version": "42df6e1d221dddc0f2acf2be37e68d553ad65f96",
"versionType": "git"
},
{
"lessThan": "568931f26af4727a51e8521f72efbc78d3b82410",
"status": "affected",
"version": "42df6e1d221dddc0f2acf2be37e68d553ad65f96",
"versionType": "git"
},
{
"lessThan": "d01c913febead04a01a5f3a6374d1f45504dc523",
"status": "affected",
"version": "42df6e1d221dddc0f2acf2be37e68d553ad65f96",
"versionType": "git"
},
{
"lessThan": "f68305267ebda7e839b5e8f77e8d77535a3d5a0f",
"status": "affected",
"version": "42df6e1d221dddc0f2acf2be37e68d553ad65f96",
"versionType": "git"
},
{
"lessThan": "d07955dd34ecae17d35d8c7d0a273a3fba653a8c",
"status": "affected",
"version": "42df6e1d221dddc0f2acf2be37e68d553ad65f96",
"versionType": "git"
}
]
},
{
"defaultStatus": "affected",
"product": "Linux",
"programFiles": [
"net/netfilter/nft_fib.c",
"net/netfilter/nft_fib_netdev.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "5.16"
},
{
"lessThan": "5.16",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"version": "6.6.148",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.101",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"version": "6.18.42",
"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": [
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.6.148",
"versionStartIncluding": "5.16",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.12.101",
"versionStartIncluding": "5.16",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.18.42",
"versionStartIncluding": "5.16",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "7.1.5",
"versionStartIncluding": "5.16",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "7.2",
"versionStartIncluding": "5.16",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: nft_fib: reject fib expression on the netdev egress hook\n\nA fib expression in a netdev egress base chain dereferences nft_in(pkt),\nNULL on the transmit path, causing a NULL pointer dereference at eval.\nnft_fib_validate() masks the hook with NF_INET_* values, but netdev hook\nnumbers are a separate enum that aliases them (NF_NETDEV_EGRESS ==\nNF_INET_LOCAL_IN), so an egress chain passes validation and then faults.\n\nAdd nft_fib_netdev_validate() that limits each result/flag to the netdev\nhook where the device it reads exists: the input-device cases (OIF,\nOIFNAME, ADDRTYPE with F_IIF) to ingress, the output-device case (ADDRTYPE\nwith F_OIF) to egress, ADDRTYPE with no device flag to both. Also restrict\nnft_fib_validate() to NFPROTO_IPV4/IPV6/INET so its NF_INET_* masks are\nnot applied to another family\u0027s hooks."
}
],
"metrics": [
{
"cvssV3_1": {
"baseScore": 7.5,
"baseSeverity": "HIGH",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
"version": "3.1"
},
"scenarios": [
{
"lang": "en",
"value": "AV:N - Once a netdev egress fib rule is installed, evaluation runs on the packet transmit datapath (nf_hook_egress in __dev_queue_xmit); a remote peer can trigger it by causing the host to send matching IPv4/IPv6 traffic through the hooked interface, matching prior netfilter CNA treatment of pre-deployed nftables rules (e.g. CVE-2026-52998).\nAC:L - No race or uncontrollable victim state is required; with an affected egress fib rule present, the attacker reliably triggers the NULL dereference on the next matching outbound packet by controlling protocol headers and normal connection traffic.\nPR:N - Runtime exploitation needs only network traffic through the netdev egress hook; although installing the fib rule requires CAP_NET_ADMIN, validation incorrectly accepts it as legal, so orchestration or administrators can deploy it and remote attackers need no target credentials or local privileges.\nUI:N - No victim interaction is required beyond ordinary network traffic processing; the kernel automatically evaluates the fib expression on egress without mounts, file opens, or user prompts.\nS:U - Impact is a kernel NULL-pointer fault and host-wide denial of service within the same kernel/network-filtering security authority; it does not constitute VM escape, IOMMU bypass, or another cross-authority boundary change.\nC:N - The failure mode is a NULL pointer dereference of nft_in(pkt) on egress (in is NULL in nf_hook_state_init); there is no use-after-free, out-of-bounds read, or other attacker-controlled memory disclosure primitive.\nI:N - The bug does not corrupt writable memory or provide control-flow hijack; it only dereferences a NULL input device pointer during fib lookup/skipping and cannot modify kernel or user data beyond the immediate fault.\nA:H - The NULL dereference in nft_fib_netdev_eval/nft_fib4_eval/nft_fib6_eval on netdev egress causes a kernel oops/panic-class fault during packet transmission, denying system availability until reboot."
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-08-17T05:42:07.408Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/4fee43759b489559a491f7c95f9bfa7a1d0c7a10"
},
{
"url": "https://git.kernel.org/stable/c/568931f26af4727a51e8521f72efbc78d3b82410"
},
{
"url": "https://git.kernel.org/stable/c/d01c913febead04a01a5f3a6374d1f45504dc523"
},
{
"url": "https://git.kernel.org/stable/c/f68305267ebda7e839b5e8f77e8d77535a3d5a0f"
},
{
"url": "https://git.kernel.org/stable/c/d07955dd34ecae17d35d8c7d0a273a3fba653a8c"
}
],
"title": "netfilter: nft_fib: reject fib expression on the netdev egress hook",
"x_generator": {
"engine": "bippy-1.2.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2026-72254",
"datePublished": "2026-08-15T05:54:42.239Z",
"dateReserved": "2026-08-09T03:40:39.915Z",
"dateUpdated": "2026-08-17T05:42:07.408Z",
"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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