---
id: CVE-2026-115391
title: >-
  Wasmtime 46.0.0 before 46.0.3 and 47.0.0 before 47.0.4 Unbounded Heap
  Allocation via WASIp3 Streams
summary: >-
  Wasmtime 46.0.0 before 46.0.3 and 47.0.0 before 47.0.4 contains an
  uncontrolled resource allocation vulnerability in its WASIp3 implementation
  that buffers guest-specified-length writes on the host without limit.
  Malicious guests can off…
severity: medium
cvss: 5.8
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:N/I:N/A:H'
cvssSource: cna
cwe:
  - CWE-770
vendor: bytecodealliance
product: wasmtime
affected:
  - wasmtime >= 46.0.0 < 46.0.3
  - wasmtime >= 47.0.0 < 47.0.4
published: '2026-10-22'
updated: '2026-10-22'
sourceUpdated: '2026-10-22T19:13:57.752Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-115391'
references:
  - url: >-
      https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-x84v-gj2h-g759
    label: GitHub Security Advisory (GHSA-x84v-gj2h-g759)
  - url: >-
      https://www.vulncheck.com/advisories/wasmtime-46.0.0-before-46.0.3-and-47.0.0-before-47.0.4-unbounded-heap-allocation-via-wasip3-streams
    label: >-
      VulnCheck Advisory: Wasmtime 46.0.0 before 46.0.3 and 47.0.0 before 47.0.4
      Unbounded Heap Allocation via WASIp3 Streams
tags:
  - cve.org
ingestedAt: '2026-10-22T22:00:50.406Z'
---

## Overview

Wasmtime 46.0.0 before 46.0.3 and 47.0.0 before 47.0.4 contains an uncontrolled resource allocation vulnerability in its WASIp3 implementation that buffers guest-specified-length writes on the host without limit. Malicious guests can offer large buffers to WASIp3 file or HTTP write streams, causing the host to copy and buffer all bytes, bounded only by guest linear memory, exhausting host memory.

## Affected

- `wasmtime >= 46.0.0 < 46.0.3`
- `wasmtime >= 47.0.0 < 47.0.4`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.