CVE-2026-44452
mediumpriority · track · 0EPSS 0.004 · 35 %ileEUUSEPSS · scored 2026-10-28
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
Technical severity, 0–10. One row per scoring source.
base score 0–10 · higher = more severe · hover a vector to decode
ssvc
A stakeholder decision — act, attend, or track — from exploitation and impact.
weaknesses
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affected products (2)
Products and version ranges known to be affected.
also known as (2)
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sources
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references (6)
External citations — patches, advisories, analysis.
- https://github.com/h2o/h2o/commit/8dc37cb1e6171f7f772667618ea440696fed82c3cnnvd
- https://github.com/h2o/h2o/security/advisories/GHSA-w68q-rqwx-7wvqcnnvd
- https://github.com/h2o/h2o/commit/8dc37cb1e6171f7f772667618ea440696fed82c3enisa_euvd
- https://github.com/h2o/h2o/security/advisories/GHSA-w68q-rqwx-7wvqenisa_euvd
- https://github.com/h2o/h2o/commit/8dc37cb1e6171f7f772667618ea440696fed82c3Patchnvd
- https://github.com/h2o/h2o/security/advisories/GHSA-w68q-rqwx-7wvqVendor Advisorynvd
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