CVE-2026-40170

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.

Affected products

Linuxmint, Rocky Linux, Ubuntu, Ngtcp2

Tatsuhiro-t ngtcp2

< 1.22.1

Fix

Available

CVSS 3.1

7.5 HIGH

EPSS

0.8% (52th percentile)

Weakness

CWE-120, CWE-121

NVD status

Modified

Published

2026-04-16

No exploit for CVE-2026-40170 has been indexed yet. Our index is built from live traffic and upstream syncs, so this page can only say what it knows — not that no exploit exists.