CVE-2026-44452
Received
Received - Intake
Zero-Length SNI Handling Denial-of-Service in h2o
Vulnerability report for CVE-2026-44452, including description, CVSS score, EPSS score, affected products, exploitability, helpful resources, and attack-flow context.
Publication date: 2026-07-16
Last updated on: 2026-07-16
Assigner: GitHub, Inc.
Description
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.
CVSS Scores
EPSS Scores
| Probability: | |
| Percentile: |
Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| h2o | h2o | to 8dc37cb (exc) |
Helpful Resources
Exploitability
CWE
KEV
| CWE ID | Description |
|---|---|
| CWE-170 | The product does not terminate or incorrectly terminates a string or array with a null character or equivalent terminator. |
| CWE-125 | The product reads data past the end, or before the beginning, of the intended buffer. |
