Description
h2o is an HTTP server with support for HTTP/1.x, HTTP/2 and HTTP/3. Prior to commit 8dc37cb, when h2o receives a ClientHello message over TLS or QUIC and it contains a zero-length SNI extension, the h2o server runs over the zero-length hostname while trying to copy the hostname, assuming that it is NULL-terminated. This is a potential denial-of-service attack vector in sense that it might trigger segmentation violation. This issue has been fixed by commit 8dc37cb.
Published: 2026-07-16
Score: 5.9 Medium
EPSS: n/a
KEV: No
Impact: n/a
Action: n/a
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History

Fri, 17 Jul 2026 00:45:00 +0000

Type Values Removed Values Added
First Time appeared H2o
H2o h2o
Vendors & Products H2o
H2o h2o

Thu, 16 Jul 2026 23:15:00 +0000

Type Values Removed Values Added
Description h2o is an HTTP server with support for HTTP/1.x, HTTP/2 and HTTP/3. Prior to commit 8dc37cb, when h2o receives a ClientHello message over TLS or QUIC and it contains a zero-length SNI extension, the h2o server runs over the zero-length hostname while trying to copy the hostname, assuming that it is NULL-terminated. This is a potential denial-of-service attack vector in sense that it might trigger segmentation violation. This issue has been fixed by commit 8dc37cb.
Title h2o is vulnerable to heap overrun
Weaknesses CWE-125
CWE-170
References
Metrics cvssV3_1

{'score': 5.9, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H'}

Subscriptions

H2o H2o
cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-07-16T22:54:42.914Z

Reserved: 2026-05-06T15:49:25.192Z

Link: CVE-2026-44452

cve-icon Vulnrichment

No data.

cve-icon NVD

No data.

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-07-17T00:30:03Z

Weaknesses