CVE-2026-35191

Issue summary: The OpenSSL QUIC server, when configured to not preform address

validation, can be forced to count incoming packets multiple times in its

unvalidated credit computation, leading to a violation of the RFC 9000

unvalidated connection amplification limit of 3 times the amount of data

received.

Impact summary: A remote attacker able to spoof packets to a server using the

OpenSSL QUIC implementation might use the server for an amplification of

a DDoS attack.

CWE: CWE-440: Expected Behavior Violation

Description: OpenSSL's QUIC stack, when operating as a server, enforces client

address validation (RFC 9000, Section 8), to confirm the peer address is not

used for a traffic amplification attack. If this feature is disabled on the

server, the QUIC stack limits the amount of server data that can be sent to 3

times the amount of data received from the peer address, until such time as the

TLS handshake is completed.

The OpenSSL QUIC server, when operating in non-validation mode, adds the

length of the whole datagram received to the unvalidated credit limit when

processing each QUIC packet in the datagram. A remote peer may,

after establishing a connection with an initial client hello frame, send a

subsequent datagram containing multiple QUIC packets, leading the server to

account the entire datagram length for each packet in the datagram, resulting

in the server believing that the peer has sent more data than it actually has,

thereby violating the 3x amplification limit mandated by the RFC.

FIPS impact: no

As the QUIC stack lives outside the FIPS module boundary, no FIPS modules

are affected by this CVE.