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7.5
ngtcp2: Large QUIC Parameter Can Crash the Server
CVE-2026-40170
Summary
A bug in ngtcp2's QUIC implementation can cause a server to crash if it receives a large QUIC parameter from a remote peer. This is fixed in version 1.22.1. If you can't update right away, you can disable logging of QUIC parameters to prevent the issue.
Original title
ngtcp2 is a C implementation of the IETF QUIC protocol. In versions prior to 1.22.1, ngtcp2_qlog_parameters_set_transport_params() serializes peer transport parameters into a fixed 1024-byte stack ...
Original description
ngtcp2 is a C implementation of the IETF QUIC protocol. In versions prior to 1.22.1, ngtcp2_qlog_parameters_set_transport_params() serializes peer transport parameters into a fixed 1024-byte stack buffer without bounds checking. When qlog is enabled, a remote peer can send sufficiently large transport parameters during the QUIC handshake to cause writes beyond the buffer boundary, resulting in a stack buffer overflow. This affects deployments that enable the qlog callback and process untrusted peer transport parameters. This issue has been fixed in version 1.22.1. If developers are unable to immediately upgrade, they can disable the qlog on client.
nvd CVSS3.1
7.5
Vulnerability type
CWE-121
Stack-based Buffer Overflow
Published: 16 Apr 2026 · Updated: 16 Apr 2026 · First seen: 16 Apr 2026