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 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.
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Exploitation outlook
- Low exploitation risk0.25% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 16% of all EPSS-scored CVEs.
Advisory coverage (1)
External references
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