GHSA-534X-F2QC-FGHV
Vulnerability from github – Published: 2026-09-03 15:32 – Updated: 2026-09-04 06:31In the Linux kernel, the following vulnerability has been resolved:
net: remove CAP_SYS_RAWIO zero-padding in dev_validate_header
dev_validate_header() reads dev->hard_header_len directly when zero-padding short link layer headers for CAP_SYS_RAWIO holders:
if (capable(CAP_SYS_RAWIO)) {
memset(ll_header + len, 0, dev->hard_header_len - len);
return true;
}
Packet send paths call dev_validate_header() on skbs whose headroom was allocated from an earlier hard_header_len read. If the device is reconfigured so that dev->hard_header_len increases before validation, the memset writes past the reserved buffer, an out-of-bounds write.
This out-of-bounds write is masked in some SOCK_RAW paths today because the same concurrent increase can first make skb_push() exceed the reserved headroom and trigger skb_under_panic(). Remove the zero-padding branch before making those hard_header_len reads consistent, so the snapshot fixes do not turn a loud panic into a silent overwrite.
This path is only reached for variable length L2 protocols, where len < hard_header_len but len >= min_header_len. No remaining in-tree variable length L2 protocol implements header_ops->validate, and the CAP_SYS_RAWIO bypass that zero-pads and accepts short headers has no real value beyond allowing testing of intentionally malformed input.
Drop the CAP_SYS_RAWIO branch. The remaining reads of dev->hard_header_len in dev_validate_header() are comparisons only and have no memory safety impact.
{
"affected": [],
"aliases": [
"CVE-2026-80731"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-09-03T13:06:11Z",
"severity": "HIGH"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: remove CAP_SYS_RAWIO zero-padding in dev_validate_header\n\ndev_validate_header() reads dev-\u003ehard_header_len directly when\nzero-padding short link layer headers for CAP_SYS_RAWIO holders:\n\n if (capable(CAP_SYS_RAWIO)) {\n memset(ll_header + len, 0, dev-\u003ehard_header_len - len);\n return true;\n }\n\nPacket send paths call dev_validate_header() on skbs whose headroom was\nallocated from an earlier hard_header_len read. If the device is\nreconfigured so that dev-\u003ehard_header_len increases before validation,\nthe memset writes past the reserved buffer, an out-of-bounds write.\n\nThis out-of-bounds write is masked in some SOCK_RAW paths today because\nthe same concurrent increase can first make skb_push() exceed the\nreserved headroom and trigger skb_under_panic(). Remove the zero-padding\nbranch before making those hard_header_len reads consistent, so the\nsnapshot fixes do not turn a loud panic into a silent overwrite.\n\nThis path is only reached for variable length L2 protocols, where\nlen \u003c hard_header_len but len \u003e= min_header_len. No remaining in-tree\nvariable length L2 protocol implements header_ops-\u003evalidate, and the\nCAP_SYS_RAWIO bypass that zero-pads and accepts short headers has no\nreal value beyond allowing testing of intentionally malformed input.\n\nDrop the CAP_SYS_RAWIO branch. The remaining reads of\ndev-\u003ehard_header_len in dev_validate_header() are comparisons only and\nhave no memory safety impact.",
"id": "GHSA-534x-f2qc-fghv",
"modified": "2026-09-04T06:31:19Z",
"published": "2026-09-03T15:32:14Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-80731"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/3b9a324e646d3657a8d9806dfbfe4f3e4066e882"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/53fd7f912c0877647d6a1e1877f5ea8535ee0b4a"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/74e035f07f53feca09e2352e77fccb09cad5e208"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/8fc9816404166a90ed8d544dc52482fafffb6d9f"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/99df6b7a713f96eda206680d100b76e15f9d9b69"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/b0f92a5731dc82556a9ae005cc35f71ab136307b"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/dbb30dc943a93e083f1e531bfdc6779e57de40d0"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/fa6d98dd925e72fc028b26a0cbbff9d2f0601ff6"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/fc902f52a02298c7432b2334c0c82a2885a1a8b6"
}
],
"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"
}
]
}
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