This vulnerability, classified as CWE‑280, CWE‑281, and CWE‑863, stems from the Wasmtime runtime’s failure to cross‑check matching FilePerms on source and destination preopens during hard‑link creation and renaming. A WASI guest that has read‑only access to a source file but lacks write permissions can therefore bypass intended access controls and overwrite host files exposed with FilePerms::READ. The result is unauthorized modification of host files, which can undermine filesystem isolation and potentially allow privilege escalation if critical files are targeted.

The flaw affects the Wasmtime runtime from bytecodealliance, specifically all releases earlier than v24.0.11, v36.0.12, v45.0.3, and v46.0.1. Any deployment of Wasmtime that allows WASI guests to access host files via the wasip1, wasip2, or wasip3 filesystem interfaces is vulnerable.

The CVSS score is 6.5, indicating moderate severity. The EPSS score of < 1% indicates a low probability of exploitation, and the vulnerability is not listed in CISA's KEV catalog. Exploitation requires that the attacker run a WebAssembly module with hard‑link or rename capabilities that target a host file exposed as read‑only, a scenario that can arise in containerized or sandboxed environments that grant the guest filesystem access. Because the flaw circumvents enforced permissions it can be used to modify critical files, but it does not allow arbitrary code execution; thus the risk is significant for environments that rely on filesystem isolation.