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Vulnerabilities CVE-2026-44452

CVE-2026-44452

Medium
Open
TLP:CLEAR

h2o is vulnerable to heap overrun

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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.

Details

CVSS Score
5.9
EPSS Score
0.25%

16.6th percentile

CVSS Vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Confidence
90%
Published
Jul 16, 2026
Last Modified
Jul 17, 2026
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