GHSA-8J84-WWJ3-JWR4
Vulnerability from github – Published: 2026-08-15 06:32 – Updated: 2026-08-17 06:33In the Linux kernel, the following vulnerability has been resolved:
vhost/net: complete zerocopy ubufs only once
vhost-net initializes one ubuf_info per outstanding zerocopy TX descriptor and hands it to the backend socket. The networking stack may then clone a zerocopy skb before all skb references are released. For example, batman-adv fragmentation reaches skb_split(), which calls skb_zerocopy_clone() and increments the same ubuf_info refcount.
vhost_zerocopy_complete() currently treats every ubuf callback as a completed vhost descriptor. It dereferences ubuf->ctx, writes the descriptor completion state, and drops the vhost_net_ubuf_ref even when the callback only releases a cloned skb reference. A backend reset can therefore wait for and free the vhost_net_ubuf_ref while another cloned skb still carries the same ubuf_info. A later completion then dereferences the freed ubufs pointer.
KASAN reports the stale completion as:
BUG: KASAN: slab-use-after-free in vhost_zerocopy_complete+0x1d7/0x1f0 BUG: KASAN: slab-use-after-free in vhost_zerocopy_complete+0x101/0x1f0 vhost_zerocopy_complete skb_copy_ubufs __dev_forward_skb2 veth_xmit
The freed object was allocated from vhost_net_ioctl() while setting the backend and freed through kfree_rcu()/kvfree_rcu_bulk after backend removal, while delayed skb completion still reached vhost_zerocopy_complete().
Honor the generic ubuf_info refcount before touching vhost state, and run the vhost descriptor completion only for the final ubuf reference. This matches the msg_zerocopy_complete() ownership rule for cloned zerocopy skbs.
{
"affected": [],
"aliases": [
"CVE-2026-74310"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-08-15T06:22:30Z",
"severity": "CRITICAL"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nvhost/net: complete zerocopy ubufs only once\n\nvhost-net initializes one ubuf_info per outstanding zerocopy TX\ndescriptor and hands it to the backend socket. The networking stack may\nthen clone a zerocopy skb before all skb references are released. For\nexample, batman-adv fragmentation reaches skb_split(), which calls\nskb_zerocopy_clone() and increments the same ubuf_info refcount.\n\nvhost_zerocopy_complete() currently treats every ubuf callback as a\ncompleted vhost descriptor. It dereferences ubuf-\u003ectx, writes the\ndescriptor completion state, and drops the vhost_net_ubuf_ref even when\nthe callback only releases a cloned skb reference. A backend reset can\ntherefore wait for and free the vhost_net_ubuf_ref while another cloned\nskb still carries the same ubuf_info. A later completion then\ndereferences the freed ubufs pointer.\n\nKASAN reports the stale completion as:\n\n BUG: KASAN: slab-use-after-free in vhost_zerocopy_complete+0x1d7/0x1f0\n BUG: KASAN: slab-use-after-free in vhost_zerocopy_complete+0x101/0x1f0\n vhost_zerocopy_complete\n skb_copy_ubufs\n __dev_forward_skb2\n veth_xmit\n\nThe freed object was allocated from vhost_net_ioctl() while setting the\nbackend and freed through kfree_rcu()/kvfree_rcu_bulk after backend\nremoval, while delayed skb completion still reached\nvhost_zerocopy_complete().\n\nHonor the generic ubuf_info refcount before touching vhost state, and run\nthe vhost descriptor completion only for the final ubuf reference. This\nmatches the msg_zerocopy_complete() ownership rule for cloned zerocopy\nskbs.",
"id": "GHSA-8j84-wwj3-jwr4",
"modified": "2026-08-17T06:33:37Z",
"published": "2026-08-15T06:32:29Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-74310"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/321c73baf54d971ce3771fea275c98a247f7ee35"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/6445b945024f4c7675ae5352b2d5885cb1deea71"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/8f6898fe80794f2d7c3d38c1158c806e4074a1c4"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/a9f8a1d2e3ff511eafd4c5462481950c2f4d2b5d"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/c069437924663539a93a1e5afe90838d9ccee284"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/ea71f873423fb73e66ad88936d6759ac0ad4aa53"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H",
"type": "CVSS_V3"
}
]
}
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