---
id: "CVE-2026-115386"
kind: "vulnerability"
aliases: ["CVE-2026-115386"]
title: "Wasmtime: directory listing leaks host memory bytes to guest programs"
severity: "low"
cvss: 2.6
epss: 0.0015
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["runtime", "rust", "self-hosted", "wasmtime", "webassembly"]
not_affected_if: ["no-preopened-directories", "trusted-guests-only", "wasip2-only"]
published_at: "2026-10-22T19:17:45+00:00"
first_seen_at: "2026-10-23T21:57:31+00:00"
updated_at: "2026-10-25T04:49:26+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-115386", "first_seen_at": "2026-10-23T21:57:31+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2026-115386", "first_seen_at": "2026-10-24T07:15:51+00:00"}]
---

# Wasmtime: directory listing leaks host memory bytes to guest programs

Wasmtime's WASIp1 fd_readdir copies uninitialized struct padding into guest memory. A guest with a preopened directory can list entries and read three bytes of leftover host stack or heap memory per entry.

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

## How to check

- Run `wasmtime --version` and compare against the fixed versions.
- Check Cargo.lock or go/npm dependency manifests for the `wasmtime` crate or bindings at versions before 36.0.17, 37.0.0 to 48.0.3, or 49.0.0 to 49.0.1.

## Fix

- Upgrade Wasmtime to `36.0.17`, `48.0.4`, or `49.0.2` depending on the release line in use.

## Timeline

- 2026-10-23T21:57:31+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-115386
- 2026-10-24T07:15:51+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2026-115386

## From the sources

Wasmtime before 36.0.17, 37.0.0 before 48.0.4, and 49.0.0 before 49.0.2 contains an information disclosure vulnerability in the WASIp1 fd_readdir implementation that copies uninitialized struct padding into guest memory. Guests with a preopened directory can list entries to receive three bytes of leftover host stack or heap memory per directory entry.

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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_