FKIE_CVE-2026-81000
Vulnerability from fkie_nvd - Published: 2026-09-11 20:19 - Updated: 2026-09-14 13:18
Severity
Summary
In the Linux kernel, the following vulnerability has been resolved:
net: tun: bound receive headroom
tun_get_user() uses tun->align both as skb headroom and when choosing how
much packet data to keep linear. OVS can propagate an oversized headroom
request from another port to TUN or TAP.
When align is larger than the usable space in a one-page skb head,
SKB_MAX_HEAD(align) underflows and the result becomes negative when stored
in good_linear. That value later wraps when assigned to the size_t linear
variable, and tun_alloc_skb() can place skb->data outside the allocated
head.
Bound the headroom stored by TUN to the one-page skb-head budget and the
largest non-sentinel 16-bit skb header offset. Leave one linear byte for
raw TUN and a complete Ethernet header for TAP, including NET_IP_ALIGN.
Also pull the raw-TUN protocol byte and the TAP Ethernet header before
accessing them, so these checks remain safe for nonlinear skbs supplied by
other allocation paths.
References
Impacted products
| Vendor | Product | Version |
|---|
{
"affected": [
{
"affectedData": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"drivers/net/tun.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"lessThan": "ad715e713610d2d5473c3a6498c825ccecf26491",
"status": "affected",
"version": "eaea34b23c46bf17b4a5638be69ab3561854f34b",
"versionType": "git"
},
{
"lessThan": "708e87937de93f445225c134a2e20519f9b4ce60",
"status": "affected",
"version": "eaea34b23c46bf17b4a5638be69ab3561854f34b",
"versionType": "git"
},
{
"lessThan": "18ef24cdb2eba32e38f1d27f2d02b7b4212e8f76",
"status": "affected",
"version": "eaea34b23c46bf17b4a5638be69ab3561854f34b",
"versionType": "git"
},
{
"lessThan": "010eee265d6bd8769b6a523d2a0693d9b3f5df43",
"status": "affected",
"version": "eaea34b23c46bf17b4a5638be69ab3561854f34b",
"versionType": "git"
},
{
"lessThan": "379d85c7f25f3e05a428225e6b8a65613c6e9b9d",
"status": "affected",
"version": "eaea34b23c46bf17b4a5638be69ab3561854f34b",
"versionType": "git"
},
{
"lessThan": "e098d9cc8859614a7f7baebc96e32a5a16b18ed2",
"status": "affected",
"version": "eaea34b23c46bf17b4a5638be69ab3561854f34b",
"versionType": "git"
},
{
"lessThan": "0ada54ea63e48b9c1608e917ccb7dfadbe86db28",
"status": "affected",
"version": "eaea34b23c46bf17b4a5638be69ab3561854f34b",
"versionType": "git"
},
{
"lessThan": "447c9303942c439a117d9b76ce6d6e2116b38ee7",
"status": "affected",
"version": "eaea34b23c46bf17b4a5638be69ab3561854f34b",
"versionType": "git"
}
]
},
{
"defaultStatus": "affected",
"product": "Linux",
"programFiles": [
"drivers/net/tun.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": "5.10.270",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.15.*",
"status": "unaffected",
"version": "5.15.221",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.1.*",
"status": "unaffected",
"version": "6.1.188",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"version": "6.6.157",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.109",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"version": "6.18.50",
"versionType": "semver"
},
{
"lessThanOrEqual": "7.2.*",
"status": "unaffected",
"version": "7.2.4",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.3-rc1",
"versionType": "original_commit_for_fix"
}
]
}
],
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
],
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: tun: bound receive headroom\n\ntun_get_user() uses tun-\u003ealign both as skb headroom and when choosing how\nmuch packet data to keep linear. OVS can propagate an oversized headroom\nrequest from another port to TUN or TAP.\n\nWhen align is larger than the usable space in a one-page skb head,\nSKB_MAX_HEAD(align) underflows and the result becomes negative when stored\nin good_linear. That value later wraps when assigned to the size_t linear\nvariable, and tun_alloc_skb() can place skb-\u003edata outside the allocated\nhead.\n\nBound the headroom stored by TUN to the one-page skb-head budget and the\nlargest non-sentinel 16-bit skb header offset. Leave one linear byte for\nraw TUN and a complete Ethernet header for TAP, including NET_IP_ALIGN.\n\nAlso pull the raw-TUN protocol byte and the TAP Ethernet header before\naccessing them, so these checks remain safe for nonlinear skbs supplied by\nother allocation paths."
}
],
"id": "CVE-2026-81000",
"lastModified": "2026-09-14T13:18:54.210",
"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": "2026-09-11T20:19:07.710",
"references": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/010eee265d6bd8769b6a523d2a0693d9b3f5df43"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/0ada54ea63e48b9c1608e917ccb7dfadbe86db28"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/18ef24cdb2eba32e38f1d27f2d02b7b4212e8f76"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/379d85c7f25f3e05a428225e6b8a65613c6e9b9d"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/447c9303942c439a117d9b76ce6d6e2116b38ee7"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/708e87937de93f445225c134a2e20519f9b4ce60"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/ad715e713610d2d5473c3a6498c825ccecf26491"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/e098d9cc8859614a7f7baebc96e32a5a16b18ed2"
}
],
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"vulnStatus": "Received"
}
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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
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- 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.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- 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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Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.
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