{"id":"CVE-2026-55368","published":"2026-11-04T22:18:06.343","lastModified":"2026-11-04T22:18:06.343","description":"h2o is an HTTP server with support for HTTP/1.x, HTTP/2 and HTTP/3. Prior to commit 48b7ae12107fd2b118e4641da49599e9aac8edd8, H2O's access-log formatter could write past its log-line buffer when an affected custom access-log format was configured. The allocation errors affected %{error}x, %q when the query string was empty, and numeric elements whose temporary terminating NUL reached the end of the buffer. A matching request could crash the server, while the effect of the one-byte NUL overwrite beyond a crash was not established. This vulnerability is fixed with commit 48b7ae12107fd2b118e4641da49599e9aac8edd8.","cvssScore":8.1,"cvssSeverity":"HIGH","cvssVector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H","cwes":["CWE-787"],"vendors":[],"products":[],"references":[{"url":"https://github.com/h2o/h2o/commit/48b7ae12107fd2b118e4641da49599e9aac8edd8","tags":[]},{"url":"https://github.com/h2o/h2o/pull/3757","tags":[]},{"url":"https://github.com/h2o/h2o/security/advisories/GHSA-m998-r5ww-rqjf","tags":[]}],"exploitRefs":[{"url":"https://github.com/h2o/h2o/commit/48b7ae12107fd2b118e4641da49599e9aac8edd8","tags":[]},{"url":"https://github.com/h2o/h2o/pull/3757","tags":[]},{"url":"https://github.com/h2o/h2o/security/advisories/GHSA-m998-r5ww-rqjf","tags":[]}],"hasPoc":true,"ai":null}