CVE-2026-44894 Netty's Default QUIC token handler accepts any client-supplied token
Attackers can bypass QUIC address validation and amplification limits by sending spoofed tokens, enabling reflection attacks against victims.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-44894?
CVE-2026-44894 is a high-severity vulnerability in Netty Netty, published on 12 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
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.
Which versions are affected by CVE-2026-44894?
2 open source packages ship an affected version, including io.netty:netty-codec-classes-quic. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
io.netty:netty-codec-classes-quic Maven | From 4.2.0.Final | 4.2.15.Final |
io.netty:netty-codec-classes-quic Maven | From 4.2.0.Final | 4.2.15.Final |
Products include Netty Netty.
How do I fix CVE-2026-44894?
Upgrade io.netty:netty-codec-classes-quic to 4.2.15.Final or later.
Is CVE-2026-44894 being exploited?
There is no known exploitation of CVE-2026-44894 in the wild and no public exploit code.
Other vulnerabilities in Netty Netty
- CVE-2026-75595 Netty: SNI Routing Bypass via Fragmented TLS ClientHello Causing Fallback to Default SslContext
- CVE-2026-75596 Netty: Fragmented ClientHello records trigger quadratic pre-handshake reassembly in default SNI parsing
- CVE-2026-59901 Netty Bzip2Decoder: Infinite Loop in RLE State Machine Leads to Event-Loop Thread Hang
- CVE-2026-55851 Netty codec-haproxy: Signed-Byte Sentinel Collision in HAProxyMessageDecoder Leads to Unbounded Memory Exhaustion
- CVE-2026-56745 Netty SpdyHttpDecoder: ByteBuf Reference Leak on RST_STREAM Leads to Native Memory Exhaustion
Sources
Also known as CLEANSTART-2026-HY47221, CLEANSTART-2026-PB26228, CLEANSTART-2026-SA68022, DEBIAN-CVE-2026-44894, ECHO-148d-a3b0-59be, GHSA-cmm3-54f8-px4j and 10 more.