CVE-2026-44452 PUBLISHED

h2o is vulnerable to heap overrun

Assigner: GitHub_M
Reserved: 06.05.2026 Published: 16.07.2026 Updated: 17.07.2026

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.

Metrics

CVSS Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
CVSS Score: 5.9

Product Status

Vendor h2o
Product h2o
Versions
  • Version < 8dc37cb is affected

References

Problem Types

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