CVE-2026-63892

Summary

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

VendorProductVersion RangeStatus
LinuxLinuxcdae7c07e3e3509eaabc18c1640a55dc5b99c179 < 37abc4504fa19d8f9f1e87792e8a2b8fdb308e40affected
LinuxLinuxcdae7c07e3e3509eaabc18c1640a55dc5b99c179 < e2d4d51cf5785815fa4e91e0c019e3eb2506a84caffected
LinuxLinuxcdae7c07e3e3509eaabc18c1640a55dc5b99c179 < de618299190b418291609e6921557253bd417e25affected
LinuxLinuxcdae7c07e3e3509eaabc18c1640a55dc5b99c179 < 5506c825f14d810f0690b1f4367cb7249ebb387aaffected
LinuxLinuxcdae7c07e3e3509eaabc18c1640a55dc5b99c179 < 542a13890b742099c461d70920e97b14e568f6ecaffected
LinuxLinuxcdae7c07e3e3509eaabc18c1640a55dc5b99c179 < d548179adcc87e1bc66b17e00352a1f536e76065affected
LinuxLinuxcdae7c07e3e3509eaabc18c1640a55dc5b99c179 < 3bec49ca55e08fb085cc4318f24b1b37eaab28cbaffected
LinuxLinuxcdae7c07e3e3509eaabc18c1640a55dc5b99c179 < de21b59c29e31c5108ddc04210631bbfab81b997affected
LinuxLinux4.15affected
LinuxLinux0 < 4.15unaffected
LinuxLinux5.10.259 <= 5.10.*unaffected
LinuxLinux5.15.210 <= 5.15.*unaffected
LinuxLinux6.1.176 <= 6.1.*unaffected
LinuxLinux6.6.143 <= 6.6.*unaffected
LinuxLinux6.12.93 <= 6.12.*unaffected
LinuxLinux6.18.35 <= 6.18.*unaffected
LinuxLinux7.0.12 <= 7.0.*unaffected
LinuxLinux7.1 <= *unaffected

Weaknesses

References