Vulnerability 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.
CVSS Score
HIGH
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Nghttp2 | Ngtcp2 | < 1.22.1 |
Related Weaknesses (CWE)
References
- https://github.com/ngtcp2/ngtcp2/commit/708a7640c1f48fb8ffb540c4b8ea5b4c1dfb8ee5Patch
- https://github.com/ngtcp2/ngtcp2/security/advisories/GHSA-f523-465f-8c8fExploitPatchVendor Advisory
- http://www.openwall.com/lists/oss-security/2026/04/17/12ExploitMailing ListPatch
- https://github.com/ngtcp2/ngtcp2/security/advisories/GHSA-f523-465f-8c8fExploitPatchVendor Advisory
FAQ
What is CVE-2026-40170?
CVE-2026-40170 is a vulnerability with a CVSS score of 7.5 (HIGH). 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 buf...
How severe is CVE-2026-40170?
CVE-2026-40170 has been rated HIGH with a CVSS base score of 7.5/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-40170?
Check the references section above for vendor advisories and patch information. Affected products include: Nghttp2 Ngtcp2.