PT-2026-33369 · Ngtcp2+2 · Ngtcp2+2

Kherrisan · Published 2026-04-16 · Updated 2026-05-28 · CVE-2026-40170

Positive Technologies (AI Summary)

CVSS v3.1

7.5

High

Base vector

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

Name of the Vulnerable Software and Affected Versions ngtcp2 versions prior to 1.22.1

Description The ngtcp2 qlog parameters set transport params() function serializes peer transport parameters into a fixed 1024-byte stack buffer without performing bounds checking. When qlog is enabled, a remote peer can send excessively large transport parameters during the QUIC handshake to cause writes beyond the buffer boundary, leading to a stack buffer overflow. This issue impacts deployments that enable the qlog callback and process untrusted peer transport parameters.

Recommendations Update to version 1.22.1. As a temporary workaround, disable qlog on the client.

Exploit

Fix

Stack Overflow

Weakness Enumeration

CWE-121

Related Identifiers

CVE-2026-40170

ECHO-C041-B4EB-D85F

OPENSUSE-SU-2026:10621-1

OPENSUSE-SU-2026:10884-1

RHSA-2026:9113

USN-8300-1

Affected Products

Linuxmint

Ubuntu

Ngtcp2

References · 26

• 🔥 https://github.com/ngtcp2/ngtcp2/security/advisories/GHSA-f523-465f-8c8f · Exploit
• https://github.com/ngtcp2/ngtcp2/commit/708a7640c1f48fb8ffb540c4b8ea5b4c1dfb8ee5 · Patch
• https://ubuntu.com/security/notices/USN-8300-1 · Vendor Advisory
• https://osv.dev/vulnerability/UBUNTU-CVE-2026-40170 · Vendor Advisory
• https://cve.org/CVERecord?id=CVE-2026-40170 · Security Note
• https://security-tracker.debian.org/tracker/CVE-2026-40170 · Vendor Advisory
• https://osv.dev/vulnerability/USN-8300-1 · Vendor Advisory
• https://nvd.nist.gov/vuln/detail/CVE-2026-40170 · Security Note
• https://ubuntu.com/security/CVE-2026-40170 · Vendor Advisory
• https://osv.dev/vulnerability/ALPINE-CVE-2026-40170 · Vendor Advisory
• https://osv.dev/vulnerability/openSUSE-SU-2026:10621-1 · Vendor Advisory
• https://osv.dev/vulnerability/openSUSE-SU-2026:10884-1 · Vendor Advisory
• http://openwall.com/lists/oss-security/2026/04/17/12 · Patch
• https://osv.dev/vulnerability/DEBIAN-CVE-2026-40170 · Vendor Advisory
• https://suse.com/security/cve/CVE-2026-40170 · Note