CVE-2026-63891
Low risk· EPSS 18%Exploitation Probability (EPSS)
Low risk18th percentile - higher than 18% of all known CVEs
Summary
In the Linux kernel Thunderbolt driver, a vulnerability was found due to missing recursion depth limit in __tb_property_parse_dir(). An unauthenticated remote attacker can send a crafted PROPERTIES_REQUEST that chains DIRECTORY entries into a back-reference loop, exhausting the kernel stack and causing a crash.
Risk Assessment
An attacker connected via Thunderbolt cable (e.g., dock, monitor, adjacent host) can trigger a kernel panic or potentially execute code in kernel context without authentication, posing a serious risk to system integrity and availability.
Recommendation
Immediately update the Linux kernel to a version containing the fix that limits recursion depth to 8 levels. If XDomain host-to-host discovery is not needed, add thunderbolt.xdomain=0 to the kernel command line.
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Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: thunderbolt: property: Cap recursion depth in __tb_property_parse_dir() A DIRECTORY entry's value field is used as the dir_offset for a recursive call into __tb_property_parse_dir() 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 PROPERTIES_REQUEST control-plane exchange can trigger this without authentication. Thread a depth counter through tb_property_parse() and __tb_property_parse_dir(), and reject blocks that exceed TB_PROPERTY_MAX_DEPTH = 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.