{"id":"CVE-2026-55213","aliases":["DEBIAN-CVE-2026-55213","EUVD-2026-43036","GHSA-432c-8xmj-frmq","UBUNTU-CVE-2026-55213"],"status":"published","title":"h2o: musl libc stack overflow (QPACK)","description":"h2o is an HTTP server with support for HTTP/1.x, HTTP/2 and HTTP/3. Prior to commit edd7a120bfc4af11ac0cbebce2a43cc1f93f9af1, when h2o processes a QPACK instruction sent from the peer over HTTP/3, lib/http3/qpack.c might allocate an on-stack buffer as large as approximately 800 KB by calling alloca, which exceeds the default pthread stack size used by musl libc and causes the h2o server to crash with a segmentation fault while touching the guard page. This issue is fixed in commit edd7a120bfc4af11ac0cbebce2a43cc1f93f9af1.","severity":{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-11","score":0.00488,"percentile":0.42458,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":false},"cwes":["CWE-789"],"published":"2026-07-10T20:49:58Z","modified":"2026-11-11T02:49:03Z","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-432c-8xmj-frmq","tags":["x_refsource_CONFIRM","advisory","report"]},{"url":"https://github.com/h2o/h2o/commit/edd7a120bfc4af11ac0cbebce2a43cc1f93f9af1","tags":["x_refsource_MISC","fix","report"]},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/55xxx/CVE-2026-55213.json","tags":["advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-55213","tags":["advisory"]},{"url":"https://security-tracker.debian.org/tracker/CVE-2026-55213","tags":["advisory"]},{"url":"https://ubuntu.com/security/CVE-2026-55213","tags":["report"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-55213","tags":["report"]}],"sources":{"cve":[{"id":"CVE-2026-55213","title":"h2o: musl libc stack overflow (QPACK)","description":"h2o is an HTTP server with support for HTTP/1.x, HTTP/2 and HTTP/3. Prior to commit edd7a120bfc4af11ac0cbebce2a43cc1f93f9af1, when h2o processes a QPACK instruction sent from the peer over HTTP/3, lib/http3/qpack.c might allocate an on-stack buffer as large as approximately 800 KB by calling alloca, which exceeds the default pthread stack size used by musl libc and causes the h2o server to crash with a segmentation fault while touching the guard page. This issue is fixed in commit edd7a120bfc4af11ac0cbebce2a43cc1f93f9af1.","status":"published","published":"2026-07-10T20:49:58.764Z","modified":"2026-07-13T14:14:45.685Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high","assessor":"cna"}],"cwes":["CWE-789"],"updated_at":"2026-11-02T14:20:11.925815Z"}],"euvd":[{"id":"EUVD-2026-43036","description":"h2o is an HTTP server with support for HTTP/1.x, HTTP/2 and HTTP/3. Prior to commit edd7a120bfc4af11ac0cbebce2a43cc1f93f9af1, when h2o processes a QPACK instruction sent from the peer over HTTP/3, lib/http3/qpack.c might allocate an on-stack buffer as large as approximately 800 KB by calling alloca, which exceeds the default pthread stack size used by musl libc and causes the h2o server to crash with a segmentation fault while touching the guard page. This issue is fixed in commit edd7a120bfc4af11ac0cbebce2a43cc1f93f9af1.","status":"published","published":"2026-07-10T20:49:58Z","modified":"2026-07-13T14:14:45Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"}],"updated_at":"2026-11-02T18:20:01.93893Z"}],"nvd":[{"id":"CVE-2026-55213","description":"h2o is an HTTP server with support for HTTP/1.x, HTTP/2 and HTTP/3. Prior to commit edd7a120bfc4af11ac0cbebce2a43cc1f93f9af1, when h2o processes a QPACK instruction sent from the peer over HTTP/3, lib/http3/qpack.c might allocate an on-stack buffer as large as approximately 800 KB by calling alloca, which exceeds the default pthread stack size used by musl libc and causes the h2o server to crash with a segmentation fault while touching the guard page. This issue is fixed in commit edd7a120bfc4af11ac0cbebce2a43cc1f93f9af1.","status":"published","published":"2026-07-10T21:16:55.497Z","modified":"2026-07-13T19:24:52.303Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high","assessor":"secondary"}],"cwes":["CWE-789"],"updated_at":"2026-11-02T14:12:28.771746Z"}],"osv":[{"id":"CVE-2026-55213","title":"h2o: musl libc stack overflow (QPACK)","description":"h2o is an HTTP server with support for HTTP/1.x, HTTP/2 and HTTP/3. Prior to commit edd7a120bfc4af11ac0cbebce2a43cc1f93f9af1, when h2o processes a QPACK instruction sent from the peer over HTTP/3, lib/http3/qpack.c might allocate an on-stack buffer as large as approximately 800 KB by calling alloca, which exceeds the default pthread stack size used by musl libc and causes the h2o server to crash with a segmentation fault while touching the guard page. This issue is fixed in commit edd7a120bfc4af11ac0cbebce2a43cc1f93f9af1.","status":"published","published":"2026-07-10T20:49:58.764Z","modified":"2026-11-11T10:47:37.780365052Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"}],"cwes":["CWE-789"],"updated_at":"2026-11-11T03:21:28.618498Z"},{"id":"DEBIAN-CVE-2026-55213","description":"h2o is an HTTP server with support for HTTP/1.x, HTTP/2 and HTTP/3. Prior to commit edd7a120bfc4af11ac0cbebce2a43cc1f93f9af1, when h2o processes a QPACK instruction sent from the peer over HTTP/3, lib/http3/qpack.c might allocate an on-stack buffer as large as approximately 800 KB by calling alloca, which exceeds the default pthread stack size used by musl libc and causes the h2o server to crash with a segmentation fault while touching the guard page. This issue is fixed in commit edd7a120bfc4af11ac0cbebce2a43cc1f93f9af1.","status":"published","published":"2026-07-10T21:16:55.497Z","modified":"2026-10-01T03:03:26.529724338Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"}],"updated_at":"2026-11-02T15:45:57.236551Z"},{"id":"UBUNTU-CVE-2026-55213","description":"h2o is an HTTP server with support for HTTP/1.x, HTTP/2 and HTTP/3. Prior to commit edd7a120bfc4af11ac0cbebce2a43cc1f93f9af1, when h2o processes a QPACK instruction sent from the peer over HTTP/3, lib/http3/qpack.c might allocate an on-stack buffer as large as approximately 800 KB by calling alloca, which exceeds the default pthread stack size used by musl libc and causes the h2o server to crash with a segmentation fault while touching the guard page. This issue is fixed in commit edd7a120bfc4af11ac0cbebce2a43cc1f93f9af1.","status":"published","published":"2026-07-10T21:16:00Z","modified":"2026-07-15T17:53:44Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"}],"updated_at":"2026-11-02T16:56:41.382716Z"}]}}