---
id: "CVE-2026-118688"
kind: "vulnerability"
aliases: ["CVE-2026-118688"]
title: "Wasmtime WASI: rename lets sandboxed guest reach host directories on macOS and FreeBSD"
severity: "high"
cvss: 8.8
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["freebsd", "macos", "package", "rust", "wasi", "wasmtime"]
not_affected_if: ["linux-only-host", "no-writable-preopens", "trusted-guest-code"]
published_at: "2026-10-28T19:17:35+00:00"
first_seen_at: "2026-10-28T19:34:56+00:00"
updated_at: "2026-10-28T19:35:42+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-118688", "first_seen_at": "2026-10-28T19:34:56+00:00"}]
---

# Wasmtime WASI: rename lets sandboxed guest reach host directories on macOS and FreeBSD

Wasmtime's wasi rename path handling re-appends a trailing slash, so renameat follows directory symlinks on macOS and FreeBSD hosts. A guest with write access to its sandbox can move host directories into it and read or write them.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the Wasmtime version in use with `wasmtime --version` or the wasmtime-wasi crate version in `Cargo.lock`
- Confirm the host OS is macOS or FreeBSD; Linux is not described as affected

## Fix

- Upgrade wasmtime-wasi to `36.0.18`, `48.0.6`, or `49.0.3` depending on release line
- Rebuild and redeploy any embedder that bundles wasmtime-wasi

## Timeline

- 2026-10-28T19:34:56+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-118688

## From the sources

wasmtime-wasi in Wasmtime before 36.0.18, 37.0.0 before 48.0.6, and 49.0.0 before 49.0.3 re-appends a trailing slash to rename source paths, causing renameat on macOS and FreeBSD hosts to follow directory symlinks. A guest with sandbox write access can rename a relative symlink such as "up/" to move host directories into its sandbox and read or write them.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_