Buffer overflow in Nghttp2 Ngtcp2
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…
Vulnerability class: Buffer Overflow
EPSS: 0.000 (6.9th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
Affected products
- Nghttp2 Ngtcp2
- Ngtcp2 — versions < 1.22.1
- Tatsuhiro-t Ngtcp2
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM, Exploit, Patch, Mitigation, Vendor Advisory)
- security-advisories@github.com (Patch, x_refsource_MISC)
- af854a3a-2127-422b-91ae-364da2661108 (Exploit, Mailing List, Patch, Third Party Advisory, Mitigation)
Frequently asked questions
- What is CVE-2026-40170?
- CVE-2026-40170 is a high-severity vulnerability in Nghttp2 Ngtcp2, classified under Stack-based Buffer Overflow. CVSS score: 7.5/10. Published 2026-04-16.
- How severe is CVE-2026-40170?
- High severity. CVSS v3 base score is 7.5 out of 10.