GHSA-489C-Q3CC-MM5R
Vulnerability from github – Published: 2026-10-18 18:31 – Updated: 2026-10-30 15:33In the Linux kernel, the following vulnerability has been resolved:
vxlan: use one headroom snapshot for neighbour replies
vxlan_na_create() samples LL_RESERVED_SPACE() to size the reply skb and then samples it again to reserve headroom. A concurrent vxlan_changelink() can update needed_headroom between the two reads, creating a TOCTOU race. The second value can exceed the allocation and make the Ethernet header write out of bounds.
The race is reproducible on the unpatched kernel. It occurred when vxlan_na_create() generated a neighbour reply while vxlan_changelink() changed the link headroom. KASAN caught a four-byte write two bytes beyond a 704-byte skbuff_small_head allocation.
Snapshot the headroom once and use that value for both allocation and reservation.
{
"affected": [],
"aliases": [
"CVE-2026-98568"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-10-18T16:17:09Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nvxlan: use one headroom snapshot for neighbour replies\n\nvxlan_na_create() samples LL_RESERVED_SPACE() to size the reply skb and then\nsamples it again to reserve headroom. A concurrent vxlan_changelink() can\nupdate needed_headroom between the two reads, creating a TOCTOU race. The\nsecond value can exceed the allocation and make the Ethernet header write out\nof bounds.\n\nThe race is reproducible on the unpatched kernel. It occurred when\nvxlan_na_create() generated a neighbour reply while vxlan_changelink() changed\nthe link headroom. KASAN caught a four-byte write two bytes beyond a 704-byte\nskbuff_small_head allocation.\n\nSnapshot the headroom once and use that value for both allocation and\nreservation.",
"id": "GHSA-489c-q3cc-mm5r",
"modified": "2026-10-30T15:33:54Z",
"published": "2026-10-18T18:31:54Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98568"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/315d42ca39f69846662961c25dcf2bb07c350d14"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/45a67662bf8ce3aa5643accf98d328dfbb47eaf6"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/481506a756dcd828ef42391cb08f38d8d96d38fc"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/9ed5a548b42d46e6968a46b67ca8a8e49b12a5a1"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/a3c5eb6e382dd426a5e7eb08608897ed57167ff7"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/e3e24f4c434c56952412f875b834aa9daaa4fb15"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/fcaf456092dc86fd5b0b523ac27ec0d114066931"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/ff022fd9d0f0282c575e11778b96bd1b637503eb"
}
],
"schema_version": "1.4.0",
"severity": []
}
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