CVE-2026-63892
thunderbolt: property: Reject dir_len < 4 to prevent size_t underflow
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.
INFO
Published Date :
July 19, 2026, 4:17 p.m.
Last Modified :
July 27, 2026, 5:44 p.m.
Remotely Exploit :
No
Source :
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Solution
- Reject dir_len values less than 4.
- Initialize lists before allocation.
- Apply provided kernel patch.
- Update Linux kernel.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-63892.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-63892 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-63892
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
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The following list is the news that have been mention
CVE-2026-63892 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-63892 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
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New CVE Received by 416baaa9-dc9f-4396-8d5f-8c081fb06d67
Jul. 19, 2026
Action Type Old Value New Value Added Affected [{'repo': 'https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git', 'vendor': 'Linux', 'product': 'Linux', 'versions': [{'status': 'affected', 'version': 'cdae7c07e3e3509eaabc18c1640a55dc5b99c179', 'lessThan': '37abc4504fa19d8f9f1e87792e8a2b8fdb308e40', 'versionType': 'git'}, {'status': 'affected', 'version': 'cdae7c07e3e3509eaabc18c1640a55dc5b99c179', 'lessThan': 'e2d4d51cf5785815fa4e91e0c019e3eb2506a84c', 'versionType': 'git'}, {'status': 'affected', 'version': 'cdae7c07e3e3509eaabc18c1640a55dc5b99c179', 'lessThan': 'de618299190b418291609e6921557253bd417e25', 'versionType': 'git'}, {'status': 'affected', 'version': 'cdae7c07e3e3509eaabc18c1640a55dc5b99c179', 'lessThan': '5506c825f14d810f0690b1f4367cb7249ebb387a', 'versionType': 'git'}, {'status': 'affected', 'version': 'cdae7c07e3e3509eaabc18c1640a55dc5b99c179', 'lessThan': '542a13890b742099c461d70920e97b14e568f6ec', 'versionType': 'git'}, {'status': 'affected', 'version': 'cdae7c07e3e3509eaabc18c1640a55dc5b99c179', 'lessThan': 'd548179adcc87e1bc66b17e00352a1f536e76065', 'versionType': 'git'}, {'status': 'affected', 'version': 'cdae7c07e3e3509eaabc18c1640a55dc5b99c179', 'lessThan': '3bec49ca55e08fb085cc4318f24b1b37eaab28cb', 'versionType': 'git'}, {'status': 'affected', 'version': 'cdae7c07e3e3509eaabc18c1640a55dc5b99c179', 'lessThan': 'de21b59c29e31c5108ddc04210631bbfab81b997', 'versionType': 'git'}], 'programFiles': ['drivers/thunderbolt/property.c'], 'defaultStatus': 'unaffected'}, {'repo': 'https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git', 'vendor': 'Linux', 'product': 'Linux', 'versions': [{'status': 'affected', 'version': '4.15'}, {'status': 'unaffected', 'version': '0', 'lessThan': '4.15', 'versionType': 'semver'}, {'status': 'unaffected', 'version': '5.10.259', 'versionType': 'semver', 'lessThanOrEqual': '5.10.*'}, {'status': 'unaffected', 'version': '5.15.210', 'versionType': 'semver', 'lessThanOrEqual': '5.15.*'}, {'status': 'unaffected', 'version': '6.1.176', 'versionType': 'semver', 'lessThanOrEqual': '6.1.*'}, {'status': 'unaffected', 'version': '6.6.143', 'versionType': 'semver', 'lessThanOrEqual': '6.6.*'}, {'status': 'unaffected', 'version': '6.12.93', 'versionType': 'semver', 'lessThanOrEqual': '6.12.*'}, {'status': 'unaffected', 'version': '6.18.35', 'versionType': 'semver', 'lessThanOrEqual': '6.18.*'}, {'status': 'unaffected', 'version': '7.0.12', 'versionType': 'semver', 'lessThanOrEqual': '7.0.*'}, {'status': 'unaffected', 'version': '7.1', 'versionType': 'original_commit_for_fix', 'lessThanOrEqual': '*'}], 'programFiles': ['drivers/thunderbolt/property.c'], 'defaultStatus': 'affected'}] Added 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. Added Reference https://git.kernel.org/stable/c/37abc4504fa19d8f9f1e87792e8a2b8fdb308e40 Added Reference https://git.kernel.org/stable/c/3bec49ca55e08fb085cc4318f24b1b37eaab28cb Added Reference https://git.kernel.org/stable/c/542a13890b742099c461d70920e97b14e568f6ec Added Reference https://git.kernel.org/stable/c/5506c825f14d810f0690b1f4367cb7249ebb387a Added Reference https://git.kernel.org/stable/c/d548179adcc87e1bc66b17e00352a1f536e76065 Added Reference https://git.kernel.org/stable/c/de21b59c29e31c5108ddc04210631bbfab81b997 Added Reference https://git.kernel.org/stable/c/de618299190b418291609e6921557253bd417e25 Added Reference https://git.kernel.org/stable/c/e2d4d51cf5785815fa4e91e0c019e3eb2506a84c