CVE-2026-50009Medium· 4.8▾ SunlitNetty: QUIC stateless reset token material exposed through header-visible connection IDs
▾ Sunlit zone — Low / medium · no exploitation signal
impact 26.4 · likelihood 0 · exploitation 0
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Exploit-prediction probability, daily snapshots since Jul 7.
Disclosure to exploitation, from the record and what we observed since indexing it.
Disclosed via GHSA
0.2%
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.
The sign-based connection ID generator (HmacSignQuicConnectionIdGenerator) and reset token generator (HmacSignQuicResetTokenGenerator) both evaluate HMAC-SHA256 with the same JVM-wide static key (io.netty.handler.codec.quic.Hmac).
During source CID rotation (QuicheQuicChannel.newSourceConnectionIds), the current server source CID C is used as input to produce the next CID N. The stateless reset token for C is defined over HMAC(K, C), specifically the first 16 bytes. The next CID N is the first L bytes of the same digest, where L = |C|.
Whenever L ≥ 16, the first 16 bytes of N are exactly the stateless reset token for C. Because N is carried in QUIC headers as a connection ID, an observer can read the headers and learn the reset token without decrypting the payload.
This directly violates RFC 9000
https://datatracker.ietf.org/doc/html/rfc9000#name-calculating-a-stateless-res: The stateless reset token MUST be difficult to guess.
Additionally https://datatracker.ietf.org/doc/html/rfc9000#name-stateless-reset-oracle
Information Disclosure and Denial of Service. An on-path attacker can obtain the stateless reset token from the connection ID header and attempt to abruptly close the client side of the connection by sending a spoofed Stateless Reset datagram.
io.netty:netty-codec-classes-quic >= 4.2.0.Final, <= 4.2.14.FinalUpgrade to a patched release:
io.netty:netty-codec-classes-quic 4.2.15.FinalConnected by shared product, vendor, weakness, or advisory.
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