CVE-2025-62711: 
Rust vulnerability analysis and mitigation

CVE-2025-62711 is a vulnerability in Wasmtime, a WebAssembly runtime developed by the Bytecode Alliance, that can cause a host crash (segfault or assert failure) when processing specially crafted WebAssembly components. The bug affects Wasmtime versions 38.0.0, 38.0.1, and 38.0.2 — introduced on 2025-10-20 and disclosed on 2025-10-24. It was patched in version 38.0.3, released the same day as disclosure. The CVSS v3.1 base score is 3.1 (Low), and the CVSS v4.0 base score is 2.1 (Low) (GitHub Advisory, Github Advisory).

The root cause (CWE-755: Improper Handling of Exceptional Conditions) stems from an incomplete refactoring introduced in PR #11592, which replaced Wasmtime's legacy setjmp/longjmp trap-handling mechanism with a Cranelift exceptions-based approach. During this transition, host-to-wasm trampolines for component-model intrinsics (e.g., resource.rep) were accidentally not updated to populate the required runtime data structures in VMStoreContext — specifically the trap handler address, stack pointer, and frame pointer fields. When a WebAssembly trap occurs during execution through one of these stale trampolines, the runtime reads an uninitialized trap handler address (defaulting to 0) and jumps to address 0x0, causing a deterministic segfault. Exploitation requires: (a) a carefully hand-crafted component using component intrinsic host-to-wasm trampolines (not produced by standard toolchains), (b) a host embedder invoking functions with the specific required component type signatures, and (c) a Wasmtime version in the 38.0.0–38.0.2 range (GitHub Advisory, Wasmtime PR #11592).

Successful exploitation causes the Wasmtime host process to crash with a segmentation fault or assertion failure, resulting in a denial of service. There is no impact on confidentiality or integrity — no data is exposed and no unauthorized modifications occur. The scope is limited to the vulnerable Wasmtime embedding; lateral movement or data exfiltration are not possible through this vulnerability (GitHub Advisory, Github Advisory).

The only remediation is to upgrade Wasmtime to version 38.0.3 or later, which correctly updates the VMStoreContext runtime data structures in component-model intrinsic trampolines. There are no configuration-based workarounds available. Users running Wasmtime 37.0.x or earlier are not affected, nor are embeddings that exclusively use core WebAssembly (not the component model). As an interim measure, operators should restrict execution to WebAssembly components from trusted sources and audit embeddings to determine whether component intrinsic type signatures are in use (GitHub Advisory, Github Advisory).

The advisory was authored and published by Wasmtime maintainer alexcrichton on 2025-10-24, who noted that the practical impact is very limited given the narrow affected version window and the highly specific exploitation conditions required. The advisory was proactively published for awareness despite the low likelihood of real-world impact, consistent with Wasmtime's security policy that the runtime should not be crashable without use of unsafe Rust (GitHub Advisory).