---
title: "CVE-2026-115889: Wasmtime - Type Confusion"
description: "Wasmtime < 36.0.19 and < 43.0.0 contains a type confusion caused by bit-packing SSA value indices overflow in Cranelift compiler backend, letting attackers cause arbitrary miscompilation and escape Wasm sandbox, exploit requires crafted Wasm functions with many SSA values."
url: https://panop.io/threat-heartbeat/CVE-2026-115889/
---

# CVE-2026-115889 Wasmtime - Type Confusion

Wasmtime < 36.0.19 and < 43.0.0 contains a type confusion caused by bit-packing SSA value indices overflow in Cranelift compiler backend, letting attackers cause arbitrary miscompilation and escape Wasm sandbox, exploit requires crafted Wasm functions with many SSA values.

CVSS base score 9.9 /10

Critical

CISA KEV

Not listed

Public exploit

None known

Authentication

Required

EPSS

0.66% chance of exploitation in 30 days

[View the NVD record ↗](https://nvd.nist.gov/vuln/detail/CVE-2026-115889)

## Details

Type

Type Confusion

Impact

Remote Code Execution, Privilege Escalation

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

Published

23 October 2026

Updated

25 October 2026

Weakness

[CWE-197](https://cwe.mitre.org/data/definitions/197.html)

## Vendor fix

Update to versions 36.0.19 or 43.0.0 or later.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

## References

- [https://nvd.nist.gov/vuln/detail/CVE-2026-115889](https://nvd.nist.gov/vuln/detail/CVE-2026-115889)
- [https://github.com/bytecodealliance/wasmtime/commit/ba8f7d70caa1825b7f64fa75cd9d03f4a438dae0](https://github.com/bytecodealliance/wasmtime/commit/ba8f7d70caa1825b7f64fa75cd9d03f4a438dae0)
- [https://github.com/bytecodealliance/wasmtime/commit/f517bd6e890c7c1291ab9fe05d8cc0c9f11e56aa](https://github.com/bytecodealliance/wasmtime/commit/f517bd6e890c7c1291ab9fe05d8cc0c9f11e56aa)
- [https://github.com/bytecodealliance/wasmtime/pull/12613](https://github.com/bytecodealliance/wasmtime/pull/12613)
- [https://github.com/bytecodealliance/wasmtime/pull/14818](https://github.com/bytecodealliance/wasmtime/pull/14818)
- [https://github.com/bytecodealliance/wasmtime/releases/tag/v36.0.19](https://github.com/bytecodealliance/wasmtime/releases/tag/v36.0.19)
- [https://github.com/bytecodealliance/wasmtime/releases/tag/v43.0.0](https://github.com/bytecodealliance/wasmtime/releases/tag/v43.0.0)
- [https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-897f-g5gm-fmxm](https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-897f-g5gm-fmxm)

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## What this record can't tell you

- Whether you run the affected software, and where
- Whether an attacker can actually reach and exploit it
- The misconfigurations that never get a CVE number
- What it would cost the business, ranked into what to fix first

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