CVE-2026-44435

Quicly: Remote Denial of Service via assertion failure when CRYPTO stream handshake data exceeds 32KB

Published Jul 16, 2026 CVSS 3.1 · 7.5 High EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared H2o
H2o quicly
Vendors & Products H2o
H2o quicly
Type Values Removed Values Added
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.
Title Quicly: Remote Denial of Service via assertion failure when CRYPTO stream handshake data exceeds 32KB
Weaknesses CWE-400
CWE-617
References
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
Jul 17, 2026, 1:02 PM
Reserved
May 6, 2026, 2:40 PM
Status
Analyzed
Published
Jul 16, 2026, 11:16 PM
Modified
Oct 24, 2026, 8:10 PM