PT-2026-60603 · H2O · H2O

CVE-2026-44452 · Published 2026-07-16 · Updated 2026-07-16

Mitre

CVSS v3.1

5.9

Medium

Base vector

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

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.

Fix

Out of bounds Read

Weakness Enumeration

CWE-170

CWE-125

Related Identifiers

CVE-2026-44452

Affected Products

H2O

References · 3

• https://nvd.nist.gov/vuln/detail/CVE-2026-44452 · Security Note
• https://github.com/h2o/h2o/commit/8dc37cb1e6171f7f772667618ea440696fed82c3 · Note
• https://github.com/h2o/h2o/security/advisories/GHSA-w68q-rqwx-7wvq · Note