---
id: "CVE-2026-115383"
kind: "vulnerability"
aliases: ["CVE-2026-115383"]
title: "Wasmtime: crafted components corrupt GC heap and crash the runtime"
severity: "medium"
cvss: 5.9
epss: 0.00183
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["plugin-hosts", "runtime", "rust", "wasm", "wasmtime"]
not_affected_if: ["exceptions-proposal-disabled", "trusted-guests-only"]
published_at: "2026-10-22T19:17:45+00:00"
first_seen_at: "2026-10-23T21:57:31+00:00"
updated_at: "2026-10-25T04:07:57+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-115383", "first_seen_at": "2026-10-23T21:57:31+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2026-115383", "first_seen_at": "2026-10-24T07:15:51+00:00"}]
---

# Wasmtime: crafted components corrupt GC heap and crash the runtime

Wasmtime versions 47.0.0 before 48.0.4 and 49.0.0 before 49.0.2 accept components whose core modules import WebAssembly tags with a subtype of the original type. A malicious guest can mis-type exception payloads to corrupt the garbage-collected heap, causing Wasmtime to panic when the exceptions proposal is enabled.

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

## How to check

- Run `wasmtime --version` and check whether it is between `47.0.0` and `48.0.4`, or between `49.0.0` and `49.0.2`.
- Check whether the embedding enables the WebAssembly exceptions proposal (unknown whether the sources name the exact setting).

## Fix

- Upgrade Wasmtime to `48.0.4` or later on the 48 line, or `49.0.2` or later on the 49 line.

## Timeline

- 2026-10-23T21:57:31+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-115383
- 2026-10-24T07:15:51+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2026-115383

## From the sources

Wasmtime 47.0.0 before 48.0.4 and 49.0.0 before 49.0.2 contains an improper validation vulnerability that accepts components whose core modules import WebAssembly tags with a subtype of the original type. Malicious guests can mis-type exception object payloads to corrupt the GC heap, causing Wasmtime to panic when the exceptions proposal is enabled.

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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_