Out-of-bounds Read in H2o
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 hos…
Vulnerability class: Buffer Overflow
CVSS v3 metric
CVSS v3 base score 5.9 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H.
Affected products
- H2o — versions < 8dc37cb
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_MISC)
- security-advisories@github.com (x_refsource_CONFIRM)
Frequently asked questions
- What is CVE-2026-44452?
- CVE-2026-44452 is a medium-severity vulnerability in H2o, classified under Out-of-bounds Read. CVSS score: 5.9/10. Published 2026-07-16.
- How severe is CVE-2026-44452?
- Medium severity. CVSS v3 base score is 5.9 out of 10.