CVE-2026-58494: Wasmtime: WASI hard links bypass wasmtime-wasi's FilePerms for destination

Wasmtime’s WASI filesystem implementation lets a guest with a read-only source file capability overwrite that file by hard-linking it into another preopen that allows file writes. An attacker who can run a WASI guest can bypass WasiCtxBuilder per-preopen FilePerms and modify host files that were exposed as FilePerms::READ.

This attack is possible through the wasip1, wasip2, and wasip3 interfaces to the WASI filesystem.

This attack is also possible through an indirection of renaming a hardlink into another preopen.