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Vulnerability record · CVE-2026-44435 · published 16 July 2026

CVE-2026-44435: H2o quicly uncontrolled resource consumption vulnerability

H2o · Quicly

Quicly is an IETF QUIC protocol implementation intended primarily for use within the H2O HTTP server. Prior to commit 937d0e9, an assertion failure is raised when the total number of valid handshake messages received over a CRYPTO stream of a single packet number space exceeds 32KB, causing a Denial of Service. This issue has been fixed by commit 937d0e9.

7.5 CVSS 3.1 High EPSS 0.49% · top 60.5% CWE-400 · Uncontrolled resource consumptionCWE-617 · CWE-617
7.5CVSS 3.1 base score
0.49%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
2References
6 Aug 2026Last modified by NVD

Description

Quicly is an IETF QUIC protocol implementation intended primarily for use within the H2O HTTP server. Prior to commit 937d0e9, an assertion failure is raised when the total number of valid handshake messages received over a CRYPTO stream of a single packet number space exceeds 32KB, causing a Denial of Service. This issue has been fixed by commit 937d0e9.

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

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/h2o/quicly/commit/937d0e9e7c669fc2bee4920632ab6aaac60e4d81 Patch
https://github.com/h2o/quicly/security/advisories/GHSA-2cw9-5673-73gv Vendor Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

7.5CVE-2026-44436H2o quicly classic buffer overflow vulnerabilityQuicly is an IETF QUIC protocol implementation intended primarily for use within the H2O HTTP server. Prior to commit 8b178e6, Quicly is vulnerable t…EPSS 0.49%7.5CVE-2026-44433H2o quicly uncontrolled resource consumption vulnerabilityQuicly is an IETF QUIC protocol implementation intended primarily for use within the H2O HTTP server. Prior to commit 8b178e6, an adversarial peer co…EPSS 0.49%7.5CVE-2025-61684H2o quicly improper input validation vulnerabilityQuicly, an IETF QUIC protocol implementation, is susceptible to a denial-of-service attack prior to commit d9d3df6a8530a102b57d840e39b0311ce5c9e14e. …EPSS 0.39%5.3CVE-2026-44434H2o quicly insufficient verification of data authenticity vulnerabilityQuicly is an IETF QUIC protocol implementation intended primarily for use within the H2O HTTP server. Prior to commit dccf5d4, Quicly was vulnerable …EPSS 0.21%7.5CVE-2026-28318SolarWinds Serv-U unauthenticated POST request denial of serviceSolarWinds Serv-U crashes when it receives a specially crafted POST request using Content-Encoding: deflate, and the crash occurs without authenticat…KEVEPSS 1.9%analysed7.5CVE-2026-45498Microsoft Defender antimalware platform uncontrolled resource consumption DoSCVE-2026-45498 is a denial of service flaw in the Microsoft Defender antimalware platform, classified as uncontrolled resource consumption (CWE-400).…KEVEPSS 1.3%analysed7.5CVE-2023-44487HTTP/2 Rapid Reset stream cancellation denial of serviceThe HTTP/2 protocol permits a client to cancel many streams quickly, and the server's handling of those resets consumes disproportionate resources. T…KEVEPSS 100%analysed7.5CVE-2023-38180Microsoft .NET and Visual Studio uncontrolled resource consumption DoSCVE-2023-38180 is a denial-of-service flaw in Microsoft .NET, ASP.NET Core and Visual Studio 2022, classified as uncontrolled resource consumption (C…KEVEPSS 14%analysed

Source: NIST National Vulnerability Database (record CVE-2026-44435), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.