CVE•Published 2026-07-16•Modified 2026-08-06•0 articles on news•4 live references•NVD data

CVE-2026-44452H2o · H2o

Vulnerability data via NVD (ingested)

CVSS v3.1

5.9

MEDIUM

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

EPSS percentile

Exploit Prediction Scoring System · top 84% of all CVEs

Weaknesses (CWE)

CWE-125Out-of-bounds Read CWE-170Improper Null Termination

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.

Timeline

Published 2026-07-16

Modified 2026-08-06

External references

NVD MITRE GitHub PoC VulnCheck

Search for exposed instances

Shodan + Censys queries derived from NVD's CPE data. The vuln tag catches assets Shodan has explicitly linked to this CVE; the product / banner fingerprints find exposed instances even when the vuln tag was never applied (which is common).

Shodan · vuln tag0 hosts

vuln:CVE-2026-44452

Hosts Shodan has explicitly fingerprinted as vulnerable.

Shodan · product

product:"H2o H2o"

All exposed H2o H2o instances — cross-reference with the CVE's affected-version range.

Shodan · banner/body mention

http.html:"H2o"

HTTP body or banner mentions "H2o" — catches deploys Shodan didn't identify as a product.

More intel sources (5)

Shodan report

vuln:CVE-2026-44452