h2o is vulnerable to heap overrun

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-44452
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-16 23:16:17 UTC
Updated2026-07-17 18:37:25 UTC
Descriptionh2o 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.

Risk And Classification

Primary CVSS: v3.1 5.9 MEDIUM from [email protected]

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS: 0.002500000 probability, percentile 0.163930000 (date 2026-07-20)

Problem Types: CWE-125 | CWE-170 | CWE-125 CWE-125: Out-of-bounds Read | CWE-170 CWE-170: Improper Null Termination

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary5.9MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
3.1CNADECLARED5.9MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA H2o H2o affected < 8dc37cb Not specified

References

ReferenceSourceLinkTags
github.com/h2o/h2o/commit/8dc37cb1e6171f7f772667618ea440696fed82c3 [email protected] github.com
github.com/h2o/h2o/security/advisories/GHSA-w68q-rqwx-7wvq [email protected] github.com
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