The vulnerability resides in the wasmtime-wasi write-zeroes operation for the default SinkOutputStream; a malicious WebAssembly guest can request arbitrarily large zero‑filled writes, causing the host to allocate unbounded memory and ultimately crash or become unresponsive. This is a classic unbounded memory allocation flaw.

Bytecode Alliance Wasmtime versions prior to 36.0.17, prior to 48.0.4 for the 37.x series, and prior to 49.0.2 for the 49.x series are affected. Any deployment that uses these versions and allows guest modules to access the default stdout/stderr sink is vulnerable.

The CVSS score of 5.9 indicates a medium risk of exploitation. An attacker could embed the vulnerable payload within a WebAssembly module, remotely or locally, depending on how the daemon is exposed. The EPSS score is not available, so current exploitation probability is unknown but the lack of a KEV listing means it is not presently known as a widely used exploit. The weakness (CWE-770) is relatively straightforward to exploit once the malicious module is loaded, but may require the host to be configured to accept unbounded writes.