CVE-2026-63892
Low risk· EPSS 13%Exploitation Probability (EPSS)
Low risk13th percentile - higher than 13% of all known CVEs
Summary
In the Linux kernel's Thunderbolt driver, a vulnerability was found due to insufficient validation of entry->length in __tb_property_parse_dir(). When length is less than 4, an out-of-bounds read and size_t underflow occur, potentially leading to system crash or code execution.
Risk Assessment
An attacker with local access to a Thunderbolt interface can send crafted data, causing out-of-bounds memory access or an infinite loop, resulting in kernel oops or privilege escalation.
Recommendation
Immediately update the Linux kernel to a version containing the fix that rejects dir_len < 4 before UUID copy. For production systems, apply the security patch available in your distribution's repository.
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Original NVD description (English source)
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.