CVE-2026-44894
HighCVSS 7.5Exploitation Probability (EPSS)
Low risk4th percentile - higher than 4% of all known CVEs
Summary
The vulnerability in the Netty library concerns the default QUIC token handler (NoQuicTokenHandler), which unconditionally accepts any token as valid. An attacker can send an Initial packet with an arbitrary token and a spoofed victim source IP, causing the server to treat the victim as validated and send full responses without the 3× amplification limit.
Risk Assessment
The risk is an amplification attack on the victim, where the Netty server sends responses (e.g., certificates) many times larger than the received packet, potentially causing network overload (DoS) for the victim.
Recommendation
Immediately update the Netty library to version 4.2.15.Final or later, which includes a fix that correctly rejects invalid tokens.
Original NVD description (English source)
Netty is a network application framework for development of protocol servers and clients. NoQuicTokenHandler is the tokenHandler used when the application does not set one. Prior to version 4.2.15.Final, its writeToken() returns false (server will not send Retry — acceptable), but validateToken() unconditionally `return 0`. In QuicheQuicServerCodec.handlePacket(), a non-negative return from validateToken() is interpreted as 'token is valid, ODCID starts at offset 0', causing the server to call quiche_accept as if the client's address had been validated by a Retry round-trip. Per RFC 9000 §8.1, a validated address lifts the 3× anti-amplification send limit. Thus any attacker who includes ANY non-empty token bytes in an Initial packet — with a spoofed victim source IP — causes the Netty server to treat the victim as validated and reflect full-size handshake flights (certificates, etc.) toward it without the 3× cap. The correct 'no token handler' semantics would be to return -1 (invalid) so the normal un-validated path and amplification limit apply. Version 4.2.15.Final patches the issue.