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

• Severity: medium (CVSS 4.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-06-12 · updated 2026-06-17
• Weakness: CWE-200

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.

Affected products

• netty: from 4.2.0 before 4.2.15 — fixed in 4.2.15

How to fix

Upgrade to a fixed version: netty 4.2.15. Check the vendor advisory for mitigations.

References

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

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