{"id":"CVE-2026-44452","aliases":["DEBIAN-CVE-2026-44452","EUVD-2026-45073","GHSA-w68q-rqwx-7wvq","UBUNTU-CVE-2026-44452"],"status":"published","title":"h2o is vulnerable to heap overrun","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.","severity":{"version":"3.1","score":5.9,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"medium","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-12","score":0.00412,"percentile":0.35979,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":false},"cwes":["CWE-125","CWE-170"],"published":"2026-07-16T22:54:42Z","modified":"2026-10-28T02:31:11Z","affected":[{"source":"osv","ecosystem":"Debian:12","package":"h2o","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.2.5+dfsg2-10","2.2.5+dfsg2-11","2.2.5+dfsg2-7","2.2.5+dfsg2-8","2.2.5+dfsg2-8.1","2.2.5+dfsg2-8.1~exp1","2.2.5+dfsg2-9"]},{"source":"osv","ecosystem":"Ubuntu:Pro:18.04:LTS","package":"h2o","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.2.3+dfsg-2","2.2.4+dfsg-1","2.2.4+dfsg-1build1","2.2.4+dfsg-1ubuntu0.1~esm2"]},{"source":"osv","ecosystem":"Ubuntu:Pro:20.04:LTS","package":"h2o","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.2.5+dfsg2-3","2.2.5+dfsg2-3build1","2.2.5+dfsg2-3ubuntu0.1~esm1"]},{"source":"osv","ecosystem":"Ubuntu:Pro:22.04:LTS","package":"h2o","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.2.5+dfsg2-6","2.2.5+dfsg2-6.1","2.2.5+dfsg2-6.1ubuntu1","2.2.5+dfsg2-6.1ubuntu2","2.2.5+dfsg2-6.1ubuntu2+esm1"]},{"source":"osv","ecosystem":"Ubuntu:24.04:LTS","package":"h2o","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.2.5+dfsg2-7","2.2.5+dfsg2-8","2.2.5+dfsg2-8.1ubuntu1","2.2.5+dfsg2-8.1ubuntu2","2.2.5+dfsg2-8.1ubuntu3"]},{"source":"osv","ecosystem":"Ubuntu:Pro:24.04:LTS","package":"dnsdist","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.8.0-1","1.8.2-1","1.8.2-2","1.8.2-3","1.8.3-1","1.8.3-2","1.8.3-2build1","1.8.3-2build2","1.8.3-2ubuntu0.1~esm1"]}],"products":[{"vendor":"h2o","product":"h2o"}],"references":[{"url":"https://github.com/h2o/h2o/security/advisories/GHSA-w68q-rqwx-7wvq","tags":["x_refsource_CONFIRM","Vendor Advisory","advisory","report"]},{"url":"https://github.com/h2o/h2o/commit/8dc37cb1e6171f7f772667618ea440696fed82c3","tags":["x_refsource_MISC","Patch","fix","report"]},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/44xxx/CVE-2026-44452.json","tags":["advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-44452","tags":["advisory"]},{"url":"https://security-tracker.debian.org/tracker/CVE-2026-44452","tags":["advisory"]},{"url":"https://ubuntu.com/security/CVE-2026-44452","tags":["report"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-44452","tags":["report"]}],"sources":{"cve":[{"id":"CVE-2026-44452","title":"h2o is vulnerable to heap overrun","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.","status":"published","published":"2026-07-16T22:54:42.914Z","modified":"2026-07-17T14:03:52.757Z","cvss":[{"version":"3.1","score":5.9,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"medium","assessor":"cna"}],"cwes":["CWE-125","CWE-170"],"updated_at":"2026-11-02T13:43:00.288193Z"}],"euvd":[{"id":"EUVD-2026-45073","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.","status":"published","published":"2026-07-16T22:54:42Z","modified":"2026-07-17T14:03:52Z","cvss":[{"version":"3.1","score":5.9,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"medium"}],"updated_at":"2026-11-02T18:19:50.846094Z"}],"nvd":[{"id":"CVE-2026-44452","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.","status":"published","published":"2026-07-16T23:16:17.28Z","modified":"2026-08-06T13:56:18.987Z","cvss":[{"version":"3.1","score":5.9,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"medium","assessor":"secondary"}],"cwes":["CWE-125","CWE-170"],"updated_at":"2026-11-02T14:12:30.250437Z"}],"osv":[{"id":"CVE-2026-44452","title":"h2o is vulnerable to heap overrun","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.","status":"published","published":"2026-07-16T22:54:42.914Z","modified":"2026-10-28T02:31:11.480308101Z","cvss":[{"version":"3.1","score":5.9,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"medium"}],"cwes":["CWE-125","CWE-170"],"updated_at":"2026-11-02T15:45:04.820169Z"},{"id":"DEBIAN-CVE-2026-44452","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.","status":"published","published":"2026-07-16T23:16:17.28Z","modified":"2026-10-01T03:03:13.614020979Z","cvss":[{"version":"3.1","score":5.9,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"medium"}],"updated_at":"2026-11-02T15:45:55.669088Z"},{"id":"UBUNTU-CVE-2026-44452","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.","status":"published","published":"2026-07-16T23:16:00Z","modified":"2026-07-29T07:57:01Z","cvss":[{"version":"3.1","score":5.9,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"medium"}],"updated_at":"2026-11-02T16:56:22.075798Z"}]}}