Executive Summary

The vulnerability CVE-2026-50009 affects Netty's QUIC implementation in versions prior to 4.2.15.Final. It involves the exposure of the stateless reset token through connection IDs visible in QUIC headers when using default HMAC-based generators. When the server rotates its source connection ID, the stateless reset token for the previous connection ID can be derived from the new connection ID. An attacker who can observe the network traffic (on-path attacker) can extract this token and use it to send a spoofed Stateless Reset packet.

This spoofed packet causes the client's connection to be abruptly terminated, resulting in a Denial of Service (DoS). The vulnerability violates RFC 9000, which requires stateless reset tokens to be difficult to guess. The issue is fixed in version 4.2.15.Final.

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Impact Analysis

This vulnerability can impact you by allowing an attacker who can observe your network traffic to disrupt your QUIC connections. Specifically, the attacker can derive the stateless reset token and send spoofed packets that abruptly terminate your connections, causing a Denial of Service (DoS).

This can lead to service disruption and reduced availability of applications relying on Netty's QUIC implementation, potentially affecting user experience and system reliability.

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Detection Guidance

This vulnerability involves the exposure of stateless reset tokens in QUIC headers when using Netty versions prior to 4.2.15.Final. Detection would require monitoring QUIC traffic for connection IDs that reveal stateless reset tokens, especially after source connection ID rotations.

Since the vulnerability is related to the QUIC protocol headers, network packet inspection tools like Wireshark or tcpdump can be used to capture QUIC traffic and analyze connection IDs for suspicious patterns that may expose reset tokens.

Specific commands to capture QUIC traffic could include:

• tcpdump -i <interface> udp port 443 -w quic_traffic.pcap
• wireshark quic_traffic.pcap (to analyze connection IDs and headers)

However, there are no explicit detection commands or tools provided in the available resources for this vulnerability.

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Mitigation Strategies

The primary mitigation step is to upgrade the affected Netty QUIC implementation to version 4.2.15.Final or later, where the issue is patched.

This update changes the default HMAC-based connection-ID and stateless-reset-token generators to prevent exposure of the reset token in QUIC headers, thereby eliminating the vulnerability.

Until the upgrade can be applied, consider restricting network access to trusted clients and monitoring for unusual Stateless Reset packets that could indicate exploitation attempts.

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Compliance Impact

The provided information does not specify any direct impact of this vulnerability on compliance with common standards and regulations such as GDPR or HIPAA.

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