CVE-2026-74684 (GCVE-0-2026-74684)
Vulnerability from cvelistv5
Published
2026-08-22 15:32
Modified
2026-08-25 05:41
Severity ?
VLAI Severity ?
EPSS score ?
Summary
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().
References
| URL | Tags | |
|---|---|---|
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Linux | Linux |
Version: 924a9bc362a5223cd448ca08c3dde21235adc310 Version: 924a9bc362a5223cd448ca08c3dde21235adc310 Version: 924a9bc362a5223cd448ca08c3dde21235adc310 Version: 924a9bc362a5223cd448ca08c3dde21235adc310 Version: ea3fb2ce5fa794d02135f5c079e05cd6fc3f545d Version: 54ef8243c3c8e90f1ea5792e6752e021a25c8eb3 Version: ca278267d6cd9544645731732455b6b20cb0e895 Version: faa3baa2828c5e1c4374f3e60041f75c64f5fcb6 Version: 99b1d3f74b9ef72c2f74c8e4c078e1bc0706e748 Version: 4.14.226 ≤ Version: 4.19.181 ≤ Version: 5.4.106 ≤ Version: 5.10.24 ≤ Version: 5.11.7 ≤ |
||
{
"containers": {
"cna": {
"affected": [
{
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"product": "Linux",
"programFiles": [
"drivers/net/tap.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
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},
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{
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"product": "Linux",
"programFiles": [
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],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "5.12"
},
{
"lessThan": "5.12",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.105",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"version": "6.18.45",
"versionType": "semver"
},
{
"lessThanOrEqual": "7.1.*",
"status": "unaffected",
"version": "7.1.9",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.2",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
{
"nodes": [
{
"cpeMatch": [
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"versionEndExcluding": "6.12.105",
"versionStartIncluding": "5.12",
"vulnerable": true
},
{
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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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{
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"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: tap: set skb-\u003edev 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-\u003edev is null\") fixed a crash in\ntap_get_user() by assigning skb-\u003edev 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-\u003edev. Without the\nassignment, a NULL pointer dereference can occur.\n\nHowever, tap_get_user_xdp() still parses the virtio-net header before\nassigning skb-\u003edev. 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-\u003edev\nis still NULL, resulting in a crash.\n\nFix this by looking up the tap device and assigning skb-\u003edev 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()."
}
],
"metrics": [
{
"cvssV3_1": {
"baseScore": 7.1,
"baseSeverity": "HIGH",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H",
"version": "3.1"
},
"scenarios": [
{
"lang": "en",
"value": "AV:L - A malicious KVM guest reaches tap_get_user_xdp() by kicking the virtio-net TX virtqueue; vhost_net handle_tx_copy batches XDP buffers and invokes tap_sendmsg(TUN_MSG_PTR), not via any host network packet-receive path.\nAC:L - On typical QEMU/KVM vhost-net+tap/macvtap backends with TX batching enabled, a guest fully controls virtio-net GSO headers and Ethernet frames; sending GSO with ethertype 0 deterministically hits dev_parse_header_protocol() with skb-\u003edev NULL without races.\nPR:N - No host root or capabilities are required; a malicious cloud VM tenant only needs code execution inside a guest using virtio-net with a vhost-net tap backend, matching other guest-to-host virtio/KVM CNA scores.\nUI:N - No separate victim action is needed; the attacker submits crafted virtio-net TX descriptors from their own guest workload during normal VM operation without requiring host administrator interaction.\nS:C - Guest-supplied virtio-net TX data triggers a NULL pointer dereference in host tap_get_user_xdp(), panicking the physical host kernel and crossing the KVM guest-to-host virtualization security boundary.\nC:N - The failure mode is a NULL pointer dereference at dev-\u003eheader_ops with skb-\u003edev unset; there is no demonstrated out-of-bounds read, use-after-free, or other memory corruption that could disclose host kernel data.\nI:N - No guest-controlled host memory write or control-flow hijack occurs; the host kernel oopses on the NULL dereference before any exploitable modification beyond the immediate crash.\nA:H - The NULL pointer dereference in dev_parse_header_protocol() provokes a host kernel oops/panic in the vhost worker during guest virtio-net TX, denying availability of the hypervisor and all co-resident VMs."
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-08-25T05:41:30.283Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/15583b07fd691a844fbf7b3ad612cdc9e9a657c0"
},
{
"url": "https://git.kernel.org/stable/c/8b444b126cd8e4473e652f529753ed4dd1360a9c"
},
{
"url": "https://git.kernel.org/stable/c/164c31ee252ebd1ac8f44c2dfc5486b6d9a0379b"
},
{
"url": "https://git.kernel.org/stable/c/3874892dd27d5387aa9a06f58d9060f18f351d24"
}
],
"title": "net: tap: set skb-\u003edev before parsing virtio net header in tap_get_user_xdp()",
"x_generator": {
"engine": "bippy-1.2.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2026-74684",
"datePublished": "2026-08-22T15:32:50.846Z",
"dateReserved": "2026-08-15T05:44:03.926Z",
"dateUpdated": "2026-08-25T05:41:30.283Z",
"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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