Vulnerabilities
- CVSS
- 5.5 Medium
- Vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H- EPSS
- 0.23%
- Risk score
- 7.5
- Published
- 2026-07-19
- Status
- Published
In 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:
1. 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]).
2. 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.
A flaw was found in the Linux kernel's Thunderbolt property driver. When processing Thunderbolt properties on a non-root path, a crafted entry with a small entry->length value can lead to an out-of-bounds read. This occurs because the kmemdup function reads beyond the intended memory block and a size_t underflow causes further out-of-bounds memory access during entry processing. This vulnerability can allow a local attacker to cause a kernel crash, resulting in a denial of service.
Coverage 5
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Advisories and references