CVE-2026-74684
Full vulnerability record from the local CVENow database.
Description
In the Linux kernel, the following vulnerability has been resolved: net: tap: set skb->dev before parsing virtio net header in tap_get_user_xdp() The commit 4f61f133f354 ("net: tap: NULL pointer derefence in dev_parse_header_protocol when skb->dev is null") fixed a crash in tap_get_user() by assigning skb->dev before calling tun_vnet_hdr_to_skb(). This is required because virtio_net_hdr_to_skb() may invoke dev_parse_header_protocol(), which dereferences skb->dev. Without the assignment, a NULL pointer dereference can occur. However, tap_get_user_xdp() still parses the virtio-net header before assigning skb->dev. When the vhost TX path passes an XDP buffer containing a GSO virtio-net header but the protocol is set to zero on purpose, tun_vnet_hdr_to_skb() can reach dev_parse_header_protocol() while skb->dev is still NULL, resulting in a crash. Fix this by looking up the tap device and assigning skb->dev before calling tun_vnet_hdr_to_skb(), matching the ordering already used in tap_get_user(). Preserve the existing RCU read-side critical section across dev_queue_xmit().
Severity
HIGH
CVSS score
7.1
(v3.1)
Vulnerability status
Received
Source identifier
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Published
2026-08-22 16:16:42.757000
Last modified
2026-10-30 13:20:03.600000
View original CVE JSON
{
"id": "CVE-2026-74684",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"published": "2026-08-22T16:16:42.757",
"lastModified": "2026-10-30T13:20:03.600",
"vulnStatus": "Received",
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: tap: set skb->dev before parsing virtio net header in tap_get_user_xdp()\n\nThe commit 4f61f133f354 (\"net: tap: NULL pointer derefence in\ndev_parse_header_protocol when skb->dev is null\") fixed a crash in\ntap_get_user() by assigning skb->dev before calling tun_vnet_hdr_to_skb().\nThis is required because virtio_net_hdr_to_skb() may invoke\ndev_parse_header_protocol(), which dereferences skb->dev. Without the\nassignment, a NULL pointer dereference can occur.\n\nHowever, tap_get_user_xdp() still parses the virtio-net header before\nassigning skb->dev. When the vhost TX path passes an XDP buffer containing\na GSO virtio-net header but the protocol is set to zero on purpose,\ntun_vnet_hdr_to_skb() can reach dev_parse_header_protocol() while skb->dev\nis still NULL, resulting in a crash.\n\nFix this by looking up the tap device and assigning skb->dev before calling\ntun_vnet_hdr_to_skb(), matching the ordering already used in\ntap_get_user(). Preserve the existing RCU read-side critical section across\ndev_queue_xmit()."
},
{
"lang": "es",
"value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nnet: tap: establecer skb -> dev antes de analizar el encabezado virtio net en tap_get_user_xdp()\n\nEl commit 4f61f133f354 ('net: tap: desreferencia de puntero NULL en dev_parse_header_protocol cuando skb -> dev es nulo') corrigió un fallo en tap_get_user() asignando skb -> dev antes de llamar a tun_vnet_hdr_to_skb(). Esto es necesario porque virtio_net_hdr_to_skb() puede invocar a dev_parse_header_protocol(), que desreferencia skb -> dev. Sin la asignación, puede ocurrir una desreferencia de puntero NULL.\n\nSin embargo, tap_get_user_xdp() todavía analiza el encabezado virtio-net antes de asignar skb -> dev. Cuando la ruta TX de vhost pasa un búfer XDP que contiene un encabezado virtio-net GSO pero el protocolo se establece a cero a propósito, tun_vnet_hdr_to_skb() puede alcanzar dev_parse_header_protocol() mientras skb -> dev todavía es NULL, lo que resulta en un fallo.\n\nSolucionar esto buscando el dispositivo tap y asignando skb -> dev antes de llamar a tun_vnet_hdr_to_skb(), igualando el orden ya utilizado en tap_get_user(). Preservar la sección crítica de lectura RCU existente a través de dev_queue_xmit()."
}
],
"affected": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"affectedData": [
{
"vendor": "Linux",
"product": "Linux",
"defaultStatus": "unaffected",
"programFiles": [
"drivers/net/tap.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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{
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{
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},
{
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{
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{
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},
{
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}
]
},
{
"vendor": "Linux",
"product": "Linux",
"defaultStatus": "affected",
"programFiles": [
"drivers/net/tap.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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"status": "affected"
},
{
"version": "0",
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"versionType": "semver",
"status": "unaffected"
},
{
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"lessThanOrEqual": "6.1.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "6.6.160",
"lessThanOrEqual": "6.6.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "6.12.105",
"lessThanOrEqual": "6.12.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "6.18.45",
"lessThanOrEqual": "6.18.*",
"versionType": "semver",
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},
{
"version": "7.1.9",
"lessThanOrEqual": "7.1.*",
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},
{
"version": "7.2",
"lessThanOrEqual": "*",
"versionType": "original_commit_for_fix",
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}
]
}
]
}
],
"metrics": {
"cvssMetricV31": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"type": "Secondary",
"cvssData": {
"version": "3.1",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H",
"baseScore": 7.1,
"baseSeverity": "HIGH",
"attackVector": "LOCAL",
"attackComplexity": "LOW",
"privilegesRequired": "NONE",
"userInteraction": "NONE",
"scope": "CHANGED",
"confidentialityImpact": "NONE",
"integrityImpact": "NONE",
"availabilityImpact": "HIGH"
},
"exploitabilityScore": 2.5,
"impactScore": 4.0
}
],
"ssvcV203": [
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"ssvcData": {
"timestamp": "2026-10-16T19:14:29.752202Z",
"id": "CVE-2026-74684",
"options": [
{
"exploitation": "none"
},
{
"automatable": "no"
},
{
"technicalImpact": "partial"
}
],
"role": "CISA Coordinator",
"version": "2.0.3"
}
}
]
},
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}