CVE-2026-40170

high

Published 2026-04-16 · Modified 2026-05-22

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CVSS v3

7.5

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS v4 NEW

—

not yet in upstream

VIR risk

7.5

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.

Predictions

Exploit likelihood

83%

Patch ETA

—

Heuristic predictions, AS-IS, for prioritization only.

Mitigations

No mitigations published for this CVE yet.

The vendor-content worker queues fetches as references arrive (check back in a few minutes). Or — if you've already worked around this in production — publish your fix to the community-verified tier.

✚ Propose a mitigation on Community → Mitigations published via the community go through AI scoring + 2 human reviewers + 7-day silent objection window before landing here with source_tier=community-verified.

OS impact

OS	Version	Status	Fixed in
sles		affected
debian	bookworm	fixed	`0.12.1+dfsg-1+deb12u1`
debian	forky	fixed	`1.22.1-1`
debian	sid	fixed	`1.22.1-1`
debian	trixie	fixed	`1.11.0-1+deb13u1`

Application impact

Vendor	Product	Versions	Fixed
tatsuhiro-t	ngtcp2	`{"endExcluding":"1.22.1"}`	`1.22.1`

References

CWEs

CWE-121

Community-verified mitigations for this CVE will appear above when contributors publish them.

Verify integrity in audit chain (admin only). AS-IS.