{"id":"CVE-2026-55367","published":"2026-11-04T22:18:06.167","lastModified":"2026-11-04T22:18:06.167","description":"h2o is an HTTP server with support for HTTP/1.x, HTTP/2 and HTTP/3. Prior to commit 4212ce114506a073505fd389db16ad2ba4e582a0, a client could send an incomplete CONNECT-UDP Capsule with an excessively large declared length, causing H2O to keep buffering received bytes without a per-Capsule limit while waiting for the remainder. Deployments that enabled proxy.connect-udp and accepted CONNECT-UDP requests could exhaust server memory and lose availability. This vulnerability is fixed with commit 4212ce114506a073505fd389db16ad2ba4e582a0.","cvssScore":7.5,"cvssSeverity":"HIGH","cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","cwes":["CWE-770"],"vendors":[],"products":[],"references":[{"url":"https://github.com/h2o/h2o/commit/4212ce114506a073505fd389db16ad2ba4e582a0","tags":[]},{"url":"https://github.com/h2o/h2o/pull/3754","tags":[]},{"url":"https://github.com/h2o/h2o/security/advisories/GHSA-q342-qp8v-p44c","tags":[]}],"exploitRefs":[{"url":"https://github.com/h2o/h2o/commit/4212ce114506a073505fd389db16ad2ba4e582a0","tags":[]},{"url":"https://github.com/h2o/h2o/pull/3754","tags":[]},{"url":"https://github.com/h2o/h2o/security/advisories/GHSA-q342-qp8v-p44c","tags":[]}],"hasPoc":true,"ai":null}