{"id":"CVE-2026-44452","summary":"h2o is vulnerable to heap overrun","details":"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.","aliases":["GHSA-w68q-rqwx-7wvq"],"modified":"2026-07-19T03:30:51.882198088Z","published":"2026-07-16T22:54:42.914Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/44xxx/CVE-2026-44452.json","unresolved_ranges":[{"extracted_events":[{"fixed":"8dc37cb"}],"source":"AFFECTED_FIELD"}],"cna_assigner":"GitHub_M","cwe_ids":["CWE-125","CWE-170"]},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/44xxx/CVE-2026-44452.json"},{"type":"ADVISORY","url":"https://github.com/h2o/h2o/security/advisories/GHSA-w68q-rqwx-7wvq"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-44452"},{"type":"FIX","url":"https://github.com/h2o/h2o/commit/8dc37cb1e6171f7f772667618ea440696fed82c3"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/h2o/h2o","events":[{"introduced":"0"},{"fixed":"8dc37cb1e6171f7f772667618ea440696fed82c3"}],"database_specific":{"source":"REFERENCES"}}],"versions":["v1.7.0","v1.7.0-beta5","v1.7.0-beta4","v1.7.0-beta3","v1.7.0-beta2","v1.7.0-beta1","v1.6.0","v1.6.0-beta2","v1.6.0-beta1","v1.5.3","v1.5.2","v1.5.1","v1.5.0","v1.5.0-beta4","v1.5.0-beta3","v1.5.0-beta2","v1.5.0-beta1","v1.4.2","v1.4.1","v1.4.0","v1.3.1","v1.3.0","v1.3.0-beta1","v1.2.0","v1.1.1","v1.1.0","v1.0.1","v0.9.2","v0.9.1"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-44452.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H"}]}