GHSA-PP6M-QVMQ-968C
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: fix vhost_get_avail_idx for a non empty ring
vhost_get_avail_idx is supposed to report whether it has updated vq->avail_idx. Instead, it returns whether all entries have been consumed, which is usually the same. But not always - in drivers/vhost/net.c and when mergeable buffers have been enabled, the driver checks whether the combined entries are big enough to store an incoming packet. If not, the driver re-enables notifications with available entries still in the ring. The incorrect return value from vhost_get_avail_idx propagates through vhost_enable_notify and causes the host to livelock if the guest is not making progress, as vhost will immediately disable notifications and retry using the available entries.
This goes back to commit d3bb267bbdcb ("vhost: cache avail index in vhost_enable_notify()") which changed vhost_enable_notify() to compare the freshly read avail index against vq->last_avail_idx instead of the previously cached vq->avail_idx. Commit 7ad472397667 ("vhost: move smp_rmb() into vhost_get_avail_idx()") then carried over the same comparison when refactoring vhost_enable_notify() to call the unified vhost_get_avail_idx().
The obvious fix is to make vhost_get_avail_idx do what the comment says it does and report whether new entries have been added.
{
"affected": [],
"aliases": [
"CVE-2026-74356"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-08-15T06:22:37Z",
"severity": "HIGH"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nvhost: fix vhost_get_avail_idx for a non empty ring\n\nvhost_get_avail_idx is supposed to report whether it has updated\nvq-\u003eavail_idx. Instead, it returns whether all entries have been\nconsumed, which is usually the same. But not always - in\ndrivers/vhost/net.c and when mergeable buffers have been enabled, the\ndriver checks whether the combined entries are big enough to store an\nincoming packet. If not, the driver re-enables notifications with\navailable entries still in the ring. The incorrect return value from\nvhost_get_avail_idx propagates through vhost_enable_notify and causes\nthe host to livelock if the guest is not making progress, as vhost will\nimmediately disable notifications and retry using the available entries.\n\nThis goes back to commit d3bb267bbdcb (\"vhost: cache avail index in\nvhost_enable_notify()\") which changed vhost_enable_notify() to compare\nthe freshly read avail index against vq-\u003elast_avail_idx instead of the\npreviously cached vq-\u003eavail_idx. Commit 7ad472397667 (\"vhost: move\nsmp_rmb() into vhost_get_avail_idx()\") then carried over the same\ncomparison when refactoring vhost_enable_notify() to call the unified\nvhost_get_avail_idx().\n\nThe obvious fix is to make vhost_get_avail_idx do what the comment\nsays it does and report whether new entries have been added.",
"id": "GHSA-pp6m-qvmq-968c",
"modified": "2026-08-17T06:33:40Z",
"published": "2026-08-15T06:32:31Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-74356"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/09861858a68342f851f71c669ac0f69865c32151"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/7f229d27bf27c7e589eca690d8612763a7a4801f"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/a9326b652bc7acd748d7a1143573845c7924d847"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/e115471008111f894c6528d9ab2ce7d0ce306f35"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H",
"type": "CVSS_V3"
}
]
}
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
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- Confirmed: The vulnerability has been validated from an analyst's perspective.
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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.
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.