CVE-2026-50009 Netty QUIC stateless reset token material exposed through header-visible connection IDs
An on-path attacker can derive stateless reset tokens from exposed connection IDs to launch Denial of Service attacks against Netty QUIC servers.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-50009?
CVE-2026-50009 is a medium-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. 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.
Which versions are affected by CVE-2026-50009?
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-2026-50009?
Upgrade io.netty:netty-codec-classes-quic to 4.2.15.Final or later.
Is CVE-2026-50009 being exploited?
There is no known exploitation of CVE-2026-50009 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-BZ13456, CLEANSTART-2026-RK84860, CLEANSTART-2026-VH61636, DEBIAN-CVE-2026-50009, ECHO-ac1d-f0e0-27f6, GHSA-cq4q-cv5g-r8q5 and 9 more.