CVE-2026-44452
🔶 mediumSummary
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 Score
5.9
Medium
EPSS Score
0.3
Exploit Probability
Published Date
2026-07-16
First Seen: 2026-07-17
📊 Relative Risk Intelligence
This CVE is Lower Risk - more severe than 32.2% of all 360,548 vulnerabilities in our database.
#244,597
Below average severity
Severity Percentile
🎯 CISA SSVC Assessment Updated: Jul 17, 2026
🔍 Exploitation Status
None
No known exploits
⚙️ Automatable
NO
Requires human interaction
💥 Technical Impact
Partial
Limited system impact
SSVC data provided by
CISA
Last Modified
2026-08-06
Source
NVD 🔗
CVSS Vector 3.1
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H