FKIE_CVE-2026-31700
Vulnerability from fkie_nvd - Published: 2026-05-01 14:16 - Updated: 2026-09-08 09:17
Severity
Summary
In the Linux kernel, the following vulnerability has been resolved:
net/packet: fix TOCTOU race on mmap'd vnet_hdr in tpacket_snd()
In tpacket_snd(), when PACKET_VNET_HDR is enabled, vnet_hdr points
directly into the mmap'd TX ring buffer shared with userspace. The
kernel validates the header via __packet_snd_vnet_parse() but then
re-reads all fields later in virtio_net_hdr_to_skb(). A concurrent
userspace thread can modify the vnet_hdr fields between validation
and use, bypassing all safety checks.
The non-TPACKET path (packet_snd()) already correctly copies vnet_hdr
to a stack-local variable. All other vnet_hdr consumers in the kernel
(tun.c, tap.c, virtio_net.c) also use stack copies. The TPACKET TX
path is the only caller of virtio_net_hdr_to_skb() that reads directly
from user-controlled shared memory.
Fix this by copying vnet_hdr from the mmap'd ring buffer to a
stack-local variable before validation and use, consistent with the
approach used in packet_snd() and all other callers.
References
Impacted products
| Vendor | Product | Version | |
|---|---|---|---|
| linux | linux_kernel | * | |
| linux | linux_kernel | * | |
| linux | linux_kernel | * | |
| linux | linux_kernel | * | |
| linux | linux_kernel | 7.1 | |
| linux | linux_kernel | 7.1 |
{
"affected": [
{
"affectedData": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"net/packet/af_packet.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"lessThan": "0f4c9754956b86de158a4af5278c5cf5bda9439e",
"status": "affected",
"version": "1d036d25e5609ba73fee6a88db01c306b140d512",
"versionType": "git"
},
{
"lessThan": "714aa973da8163925eda7efd49361ccbee21ee46",
"status": "affected",
"version": "1d036d25e5609ba73fee6a88db01c306b140d512",
"versionType": "git"
},
{
"lessThan": "1490f82353bdabc09265a74e645b07f05cf4188e",
"status": "affected",
"version": "1d036d25e5609ba73fee6a88db01c306b140d512",
"versionType": "git"
},
{
"lessThan": "74e2db36fe50e3ad9d5300d7fd0e6e2a15a6d121",
"status": "affected",
"version": "1d036d25e5609ba73fee6a88db01c306b140d512",
"versionType": "git"
},
{
"lessThan": "3a1bf9116ea31470b89692585c3910dfe830dcdd",
"status": "affected",
"version": "1d036d25e5609ba73fee6a88db01c306b140d512",
"versionType": "git"
},
{
"lessThan": "28324a3b62d9ce7f9bdd65a8ce63f382041d1b27",
"status": "affected",
"version": "1d036d25e5609ba73fee6a88db01c306b140d512",
"versionType": "git"
},
{
"lessThan": "48a6ef291a17639e1b6ae0fbe9c8b2bb87d7804b",
"status": "affected",
"version": "1d036d25e5609ba73fee6a88db01c306b140d512",
"versionType": "git"
},
{
"lessThan": "2c054e17d9d41f1020376806c7f750834ced4dc5",
"status": "affected",
"version": "1d036d25e5609ba73fee6a88db01c306b140d512",
"versionType": "git"
}
]
},
{
"defaultStatus": "affected",
"product": "Linux",
"programFiles": [
"net/packet/af_packet.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "4.6"
},
{
"lessThan": "4.6",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.10.*",
"status": "unaffected",
"version": "5.10.259",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.15.*",
"status": "unaffected",
"version": "5.15.210",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.1.*",
"status": "unaffected",
"version": "6.1.176",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"version": "6.6.136",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.84",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"version": "6.18.25",
"versionType": "semver"
},
{
"lessThanOrEqual": "7.0.*",
"status": "unaffected",
"version": "7.0.2",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.1",
"versionType": "original_commit_for_fix"
}
]
}
],
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"affectedData": [
{
"defaultStatus": "unknown",
"product": "SIMATIC S7-1500 CPU 1518-4 PN/DP MFP",
"vendor": "Siemens",
"versions": [
{
"lessThan": "*",
"status": "affected",
"version": "V3.1.6",
"versionType": "custom"
}
]
},
{
"defaultStatus": "unknown",
"product": "SIMATIC S7-1500 CPU 1518-4 PN/DP MFP",
"vendor": "Siemens",
"versions": [
{
"lessThan": "*",
"status": "affected",
"version": "V3.1.6",
"versionType": "custom"
}
]
},
{
"defaultStatus": "unknown",
"product": "SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP",
"vendor": "Siemens",
"versions": [
{
"lessThan": "*",
"status": "affected",
"version": "V3.1.6",
"versionType": "custom"
}
]
},
{
"defaultStatus": "unknown",
"product": "SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP",
"vendor": "Siemens",
"versions": [
{
"lessThan": "*",
"status": "affected",
"version": "V3.1.6",
"versionType": "custom"
}
]
},
{
"defaultStatus": "unknown",
"product": "SIPLUS S7-1500 CPU 1518-4 PN/DP MFP",
"vendor": "Siemens",
"versions": [
{
"lessThan": "*",
"status": "affected",
"version": "V3.1.6",
"versionType": "custom"
}
]
}
],
"source": "0b142b55-0307-4c5a-b3c9-f314f3fb7c5e"
}
],
"configurations": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"matchCriteriaId": "7A6CE177-C7BA-4E34-9D61-035565B5FFF5",
"versionEndExcluding": "6.6.136",
"versionStartIncluding": "4.6",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"matchCriteriaId": "D4ECA0DE-AFF5-4688-B219-4CA2336CA5B7",
"versionEndExcluding": "6.12.84",
"versionStartIncluding": "6.7",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"matchCriteriaId": "8B0A7E0E-F6D8-45DB-8CD9-01839FE40A6C",
"versionEndExcluding": "6.18.25",
"versionStartIncluding": "6.13",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"matchCriteriaId": "1BD58F1E-7C20-4C0D-92A2-FAC5CBFBE8A8",
"versionEndExcluding": "7.0.2",
"versionStartIncluding": "6.19",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:7.1:rc1:*:*:*:*:*:*",
"matchCriteriaId": "B1EF7059-E670-45F4-B422-54C40FA86390",
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},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:7.1:rc2:*:*:*:*:*:*",
"matchCriteriaId": "0D38F0BF-A728-4133-A358-D44A2F7EE6D6",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
]
}
],
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/packet: fix TOCTOU race on mmap\u0027d vnet_hdr in tpacket_snd()\n\nIn tpacket_snd(), when PACKET_VNET_HDR is enabled, vnet_hdr points\ndirectly into the mmap\u0027d TX ring buffer shared with userspace. The\nkernel validates the header via __packet_snd_vnet_parse() but then\nre-reads all fields later in virtio_net_hdr_to_skb(). A concurrent\nuserspace thread can modify the vnet_hdr fields between validation\nand use, bypassing all safety checks.\n\nThe non-TPACKET path (packet_snd()) already correctly copies vnet_hdr\nto a stack-local variable. All other vnet_hdr consumers in the kernel\n(tun.c, tap.c, virtio_net.c) also use stack copies. The TPACKET TX\npath is the only caller of virtio_net_hdr_to_skb() that reads directly\nfrom user-controlled shared memory.\n\nFix this by copying vnet_hdr from the mmap\u0027d ring buffer to a\nstack-local variable before validation and use, consistent with the\napproach used in packet_snd() and all other callers."
}
],
"id": "CVE-2026-31700",
"lastModified": "2026-09-08T09:17:59.693",
"metrics": {
"cvssMetricV31": [
{
"cvssData": {
"attackComplexity": "LOW",
"attackVector": "LOCAL",
"availabilityImpact": "HIGH",
"baseScore": 7.8,
"baseSeverity": "HIGH",
"confidentialityImpact": "HIGH",
"integrityImpact": "HIGH",
"privilegesRequired": "LOW",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
},
"exploitabilityScore": 1.8,
"impactScore": 5.9,
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"type": "Secondary"
}
]
},
"published": "2026-05-01T14:16:19.907",
"references": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/0f4c9754956b86de158a4af5278c5cf5bda9439e"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/1490f82353bdabc09265a74e645b07f05cf4188e"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"tags": [
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"url": "https://git.kernel.org/stable/c/28324a3b62d9ce7f9bdd65a8ce63f382041d1b27"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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},
{
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{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"tags": [
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"url": "https://git.kernel.org/stable/c/48a6ef291a17639e1b6ae0fbe9c8b2bb87d7804b"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/714aa973da8163925eda7efd49361ccbee21ee46"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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"url": "https://git.kernel.org/stable/c/74e2db36fe50e3ad9d5300d7fd0e6e2a15a6d121"
},
{
"source": "0b142b55-0307-4c5a-b3c9-f314f3fb7c5e",
"url": "https://cert-portal.siemens.com/productcert/html/ssa-019113.html"
}
],
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"vulnStatus": "Modified",
"weaknesses": [
{
"description": [
{
"lang": "en",
"value": "CWE-362"
}
],
"source": "nvd@nist.gov",
"type": "Primary"
}
]
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
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- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
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- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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