GHSA-CX83-HXFR-M85V
Vulnerability from github – Published: 2026-06-25 09:31 – Updated: 2026-06-28 09:31In the Linux kernel, the following vulnerability has been resolved:
xsk: cache csum_start/csum_offset to fix TOCTOU in xsk_skb_metadata()
The TX metadata area resides in the UMEM buffer which is memory-mapped and concurrently writable by userspace. In xsk_skb_metadata(), csum_start and csum_offset are read from shared memory for bounds validation, then read again for skb assignment. A malicious userspace application can race to overwrite these values between the two reads, bypassing the bounds check and causing out-of-bounds memory access during checksum computation in the transmit path.
Fix this by reading csum_start and csum_offset into local variables once, then using the local copies for both validation and assignment.
Note that other metadata fields (flags, launch_time) and the cached csum fields may be mutually inconsistent due to concurrent userspace writes, but this is benign: the only security-critical invariant is that each field's validated value is the same one used, which local caching guarantees.
{
"affected": [],
"aliases": [
"CVE-2026-53250"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-06-25T09:16:42Z",
"severity": "HIGH"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nxsk: cache csum_start/csum_offset to fix TOCTOU in xsk_skb_metadata()\n\nThe TX metadata area resides in the UMEM buffer which is memory-mapped\nand concurrently writable by userspace. In xsk_skb_metadata(),\ncsum_start and csum_offset are read from shared memory for bounds\nvalidation, then read again for skb assignment. A malicious userspace\napplication can race to overwrite these values between the two reads,\nbypassing the bounds check and causing out-of-bounds memory access\nduring checksum computation in the transmit path.\n\nFix this by reading csum_start and csum_offset into local variables\nonce, then using the local copies for both validation and assignment.\n\nNote that other metadata fields (flags, launch_time) and the cached\ncsum fields may be mutually inconsistent due to concurrent userspace\nwrites, but this is benign: the only security-critical invariant is\nthat each field\u0027s validated value is the same one used, which local\ncaching guarantees.",
"id": "GHSA-cx83-hxfr-m85v",
"modified": "2026-06-28T09:31:46Z",
"published": "2026-06-25T09:31:22Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-53250"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/0dfe05b938435892875e07771170051346412df9"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/22ba97ea9cc1f63a0d0244fae38057ed452b6ac7"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/bfdfd2706d5fb2cd496a1506e680daf979309c8b"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
}
]
}
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
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- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.