CVE-2026-44452

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.

CVSS v3 5.9 MEDIUM

5.9^/10

CVSS v3 : MEDIUM

Vector :

Exploitability : 2.2 / Impact : 3.6

Attack Vector NETWORK

Attack Complexity HIGH

Privileges Required NONE

User Interaction NONE

Confidentiality Impact NONE

Integrity Impact NONE

Availability Impact HIGH

Scope UNCHANGED

References

Link	Resource
https://github.com/h2o/h2o/commit/8dc37cb1e6171f7f772667618ea440696fed82c3	Patch
https://github.com/h2o/h2o/security/advisories/GHSA-w68q-rqwx-7wvq	Vendor Advisory

Configurations

Configuration 1 (hide)

cpe:2.3:a:h2o:h2o:*:*:*:*:*:*:*:*

History

No history.

Information

Published : 2026-07-16 23:16

Updated : 2026-08-06 13:56

NVD link : CVE-2026-44452

Mitre link : CVE-2026-44452

CVE.ORG link : CVE-2026-44452

JSON object : View

Products Affected

h2o

h2o

CWE

CWE-125

Out-of-bounds Read

CWE-170

Improper Null Termination

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