---
id: "CVE-2026-119140"
kind: "vulnerability"
aliases: ["CVE-2026-119140"]
title: "Wasmtime: malicious component can crash host via thread.yield"
severity: "medium"
cvss: 5.9
epss: null
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["embedders", "runtime", "rust", "wasmtime", "webassembly"]
not_affected_if: ["fixed-version", "trusted-components-only"]
published_at: "2026-10-29T16:18:07+00:00"
first_seen_at: "2026-10-29T16:25:58+00:00"
updated_at: "2026-10-29T16:31:35+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-119140", "first_seen_at": "2026-10-29T16:25:58+00:00"}]
---

# Wasmtime: malicious component can crash host via thread.yield

Wasmtime versions 46.0.0 before 48.0.6 and 49.0.0 before 49.0.3 let a malicious WebAssembly component panic the host process through thread.yield in a start function. The attacker only gets a denial of service that crashes applications embedding Wasmtime.

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

## How to check

- Check the Wasmtime version in your dependencies, for example `wasmtime --version` or the wasmtime entry in Cargo.lock.
- Look for embedders that load untrusted components and call their start functions.

## Fix

- Wasmtime `48.0.6`
- Wasmtime `49.0.3`

## Timeline

- 2026-10-29T16:25:58+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-119140

## From the sources

Wasmtime 46.0.0 before 48.0.6 and 49.0.0 before 49.0.3 contains a denial of service vulnerability that allows malicious components to panic the host via thread.yield in start functions. Attackers can supply a component whose start function calls an async-lowered import then thread.yield, causing an undisposed fiber drop that crashes embedders.

---

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