GHSA-C25W-638M-WRP7
Vulnerability from github – Published: 2026-07-19 18:31 – Updated: 2026-07-19 18:31In the Linux kernel, the following vulnerability has been resolved:
thunderbolt: property: Reject dir_len < 4 to prevent size_t underflow
On the non-root path, __tb_property_parse_dir() takes dir_len from entry->length (u16 widened to size_t). Two distinct OOB conditions follow when entry->length < 4:
-
The non-root path begins with kmemdup(&block[dir_offset], sizeof(*dir->uuid), ...) which always reads 4 dwords from dir_offset. tb_property_entry_valid() only enforces dir_offset + entry->length <= block_len, so a crafted entry with dir_offset close to the end of the property block and entry->length in 0..3 passes that gate but lets the UUID copy run off the block (e.g. dir_offset = 497, dir_len = 3 in a 500-dword block reads block[497..501]).
-
After the kmemdup, content_len = dir_len - 4 underflows size_t to ~SIZE_MAX, nentries becomes SIZE_MAX / 4, and the entry walk runs OOB on each iteration until an entry fails validation or the kernel oopses on an unmapped page.
Reject dir_len < 4 on the non-root path before the UUID kmemdup, which closes both holes.
Also move INIT_LIST_HEAD(&dir->properties) up to immediately after the dir allocation so the new error-return path (and the existing uuid-alloc failure path) calling tb_property_free_dir() sees a walkable list rather than the zero-initialized NULL next/prev that list_for_each_entry_safe() would oops on.
{
"affected": [],
"aliases": [
"CVE-2026-63892"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-07-19T16:17:06Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nthunderbolt: property: Reject dir_len \u003c 4 to prevent size_t underflow\n\nOn the non-root path, __tb_property_parse_dir() takes dir_len from\nentry-\u003elength (u16 widened to size_t). Two distinct OOB conditions\nfollow when entry-\u003elength \u003c 4:\n\n1. The non-root path begins with kmemdup(\u0026block[dir_offset],\n sizeof(*dir-\u003euuid), ...) which always reads 4 dwords from\n dir_offset. tb_property_entry_valid() only enforces\n dir_offset + entry-\u003elength \u003c= block_len, so a crafted entry\n with dir_offset close to the end of the property block and\n entry-\u003elength in 0..3 passes that gate but lets the UUID copy\n run off the block (e.g. dir_offset = 497, dir_len = 3 in a\n 500-dword block reads block[497..501]).\n\n2. After the kmemdup, content_len = dir_len - 4 underflows size_t\n to ~SIZE_MAX, nentries becomes SIZE_MAX / 4, and the entry\n walk runs OOB on each iteration until an entry fails\n validation or the kernel oopses on an unmapped page.\n\nReject dir_len \u003c 4 on the non-root path *before* the UUID kmemdup,\nwhich closes both holes.\n\nAlso move INIT_LIST_HEAD(\u0026dir-\u003eproperties) up to immediately after\nthe dir allocation so the new error-return path (and the existing\nuuid-alloc failure path) calling tb_property_free_dir() sees a\nwalkable list rather than the zero-initialized NULL next/prev that\nlist_for_each_entry_safe() would oops on.",
"id": "GHSA-c25w-638m-wrp7",
"modified": "2026-07-19T18:31:44Z",
"published": "2026-07-19T18:31:44Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-63892"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/37abc4504fa19d8f9f1e87792e8a2b8fdb308e40"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/3bec49ca55e08fb085cc4318f24b1b37eaab28cb"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/542a13890b742099c461d70920e97b14e568f6ec"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/5506c825f14d810f0690b1f4367cb7249ebb387a"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/d548179adcc87e1bc66b17e00352a1f536e76065"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/de21b59c29e31c5108ddc04210631bbfab81b997"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/de618299190b418291609e6921557253bd417e25"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/e2d4d51cf5785815fa4e91e0c019e3eb2506a84c"
}
],
"schema_version": "1.4.0",
"severity": []
}
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