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Linux azure: In the Linux kernel, the following vulnerability has been resolved: thunderbolt: property: Reject dir_len < 4 to prevent size_t underflow On the… (CVE-2026-63892)

0
Medium
Published: 07/20/2026 (07/20/2026, 00:00:00 UTC)
Source: GCVE Database
Product: linux-azure

Description

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.

Affected software

Affected versions
<7.0.0-28.28~24.04.1<7.0.0-1016.16~24.04.1<7.0.0-28.28.1~24.04.3<7.0.0-28.28<7.0.0-1009.9

Technical Details

Gcve Source
db.gcve.eu
Osv Id
GHSA-c25w-638m-wrp7
Osv Schema Version
1.4.0
Aliases
["CVE-2026-63892"]
Ecosystems
[]
Database Specific Severity
null
Cvss Version
null

Threat ID: 6a5d27ab2a4a8d598912ff88

Added to database: 07/19/2026, 19:38:19 UTC

Last enriched: 07/19/2026, 20:12:00 UTC

Last updated: 09/02/2026, 22:52:13 UTC

Views: 52

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