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CVE-2026-40170

7.5 · HIGH

ngtcp2 is a C implementation of the IETF QUIC protocol.

Published Apr 16, 2026CWE-121EPSS 0.95%

Overview

CVE-2026-40170 is a high-severity vulnerability. It was published on April 16, 2026 and has a CVSS 3.1 base score of 7.5 (HIGH).

This vulnerability has a CVSS 3.1 base score of 7.5, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical 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.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

GitHubgithub.com/ngtcp2/ngtcp2/commit/708a7640c1f48fb8ffb540c4b8ea5b4c1dfb8ee5GitHubgithub.com/ngtcp2/ngtcp2/security/advisories/GHSA-f523-465f-8c8fRefwww.openwall.com/lists/oss-security/2026/04/17/12Refaccess.redhat.com/errata/RHSA-2026:22963Refaccess.redhat.com/errata/RHSA-2026:25049Refaccess.redhat.com/errata/RHSA-2026:9113Refaccess.redhat.com/security/cve/CVE-2026-40170Refbugzilla.redhat.com/show_bug.cgi?id=2459061GitHubgithub.com/ngtcp2/ngtcp2/security/advisories/GHSA-f523-465f-8c8fRefsecurity.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-40170.json

How CyberStrike helps

Frequently asked questions

What is CVE-2026-40170?

CVE-2026-40170 is a high-severity vulnerability. It was published on April 16, 2026 and has a CVSS 3.1 base score of 7.5 (HIGH).

How severe is CVE-2026-40170?

This vulnerability has a CVSS 3.1 base score of 7.5, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2026-40170?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-40170?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-40170 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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