CVE-2026-63891

In the Linux kernel, the following vulnerability has been resolved:

thunderbolt: property: Cap recursion depth in _tbpropertyparsedir()

A DIRECTORY entry's value field is used as the dir_offset for a recursive call into __tbpropertyparsedir() with no depth counter. A crafted peer that chains DIRECTORY entries into a back-reference loop drives the parser until the kernel stack is exhausted and the guard page fires. Any untrusted XDomain peer (cable, dock, in-line inspector, adjacent host) that reaches the PROPERTIESREQUEST control-plane exchange can trigger this without authentication.

Thread a depth counter through tbpropertyparse() and __tbpropertyparsedir(), and reject blocks that exceed TBPROPERTYMAXDEPTH = 8. That is comfortably larger than any observed legitimate XDomain layout.

Operators who do not need XDomain host-to-host discovery can disable the path entirely with thunderbolt.xdomain=0 on the kernel command line.