---
id: "CVE-2026-115384"
kind: "vulnerability"
aliases: ["CVE-2026-115384"]
title: "Wasmtime: malicious guest components overflow host stack and escape sandbox"
severity: "critical"
cvss: 9.9
epss: 0.00312
exploited: false
status: "resolved"
category: "package"
products: [{"name": "wasmtime", "fixed": ["48.0.4", "49.0.2"], "affected": ">= 39.0.0, < 48.0.4; >= 49.0.0, < 49.0.2", "ecosystem": "crates.io"}]
ecosystems: ["crates.io"]
tags: ["component-model-async", "package", "runtime", "rust", "sandbox-escape", "self-hosted", "wasmtime", "webassembly"]
not_affected_if: ["default-config", "no-untrusted-components"]
published_at: "2026-10-22T19:17:45+00:00"
first_seen_at: "2026-10-23T21:57:31+00:00"
updated_at: "2026-10-24T07:15:51+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-115384", "first_seen_at": "2026-10-23T21:57:31+00:00"}, {"source": "analyst", "url": null, "first_seen_at": "2026-10-23T22:22:55+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2026-115384", "first_seen_at": "2026-10-24T07:15:51+00:00"}]
---

# Wasmtime: malicious guest components overflow host stack and escape sandbox

Wasmtime versions 39.0.0 through 48.0.3 and 49.0.0 through 49.0.1 fail to validate async callback result types in the component model. A malicious guest component can write about 16KB onto the native host stack, overwriting return addresses to crash the host or escape the WebAssembly sandbox.

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

## Affected

- crates.io:wasmtime affected >= 39.0.0, < 48.0.4; >= 49.0.0, < 49.0.2 fixed 48.0.4, 49.0.2

## How to check

Run wasmtime --version and check whether it falls in 39.0.0-48.0.3 or 49.0.0-49.0.1, or check Cargo.lock for wasmtime entries in those ranges.

## Fix

Upgrade to wasmtime 48.0.4 or 49.0.2 (or any later release).
If you cannot upgrade, do not run untrusted component-model-async guests (sources do not give a workaround).

## Timeline

- 2026-10-23T21:57:31+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-115384
- 2026-10-23T22:22:55+00:00 analyst — Read Wasmtime GHSA-32h6-97mm-8q3c (published Oct 2, vendor CVSS 4.0 9.3; NVD 9.9 by VulnCheck) plus RustSec and 49.0.2 release notes. Affected >=39.0.0,<48.0.4 and >=49.0.0,<49.0.2. Workaround: disable component-model-async. No PoC or exploitation found; I did not search social posts. Note the 40-47 versions are inside the affected range.
- 2026-10-24T07:15:51+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2026-115384

## Documents

- [advisory] GHSA-32h6-97mm-8q3c Wasmtime async-lifted callback stack overflow https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-32h6-97mm-8q3c
- [advisory] RUSTSEC-2026-0327 https://rustsec.org/advisories/RUSTSEC-2026-0327
- [fix] Wasmtime 49.0.2 release notes https://sourceforge.net/projects/wasmtime.mirror/files/v49.0.2/

## From the sources

Wasmtime 39.0.0 before 48.0.4 and 49.0.0 before 49.0.2 contains a stack buffer overflow vulnerability that allows malicious guests to write ~16KB to the native stack via unvalidated async callback result types. Attackers can supply components with mistyped component-model-async callback functions to overwrite return addresses, crashing the host or escaping the sandbox.

---

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