{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-55368","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","state":"PUBLISHED","assignerShortName":"GitHub_M","dateReserved":"2026-06-16T18:57:40.181Z","datePublished":"2026-11-04T21:38:04.613Z","dateUpdated":"2026-11-04T21:38:04.613Z"},"containers":{"cna":{"title":"h2o: buffer overflow when using the %{error}x log directive","problemTypes":[{"descriptions":[{"cweId":"CWE-787","lang":"en","description":"CWE-787: Out-of-bounds Write","type":"CWE"}]}],"metrics":[{"cvssV3_1":{"attackComplexity":"HIGH","attackVector":"NETWORK","availabilityImpact":"HIGH","baseScore":8.1,"baseSeverity":"HIGH","confidentialityImpact":"HIGH","integrityImpact":"HIGH","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H","version":"3.1"}}],"references":[{"name":"https://github.com/h2o/h2o/security/advisories/GHSA-m998-r5ww-rqjf","tags":["x_refsource_CONFIRM"],"url":"https://github.com/h2o/h2o/security/advisories/GHSA-m998-r5ww-rqjf"},{"name":"https://github.com/h2o/h2o/pull/3757","tags":["x_refsource_MISC"],"url":"https://github.com/h2o/h2o/pull/3757"},{"name":"https://github.com/h2o/h2o/commit/48b7ae12107fd2b118e4641da49599e9aac8edd8","tags":["x_refsource_MISC"],"url":"https://github.com/h2o/h2o/commit/48b7ae12107fd2b118e4641da49599e9aac8edd8"}],"affected":[{"vendor":"h2o","product":"h2o","versions":[{"version":"< 48b7ae12107fd2b118e4641da49599e9aac8edd8","status":"affected"}]}],"providerMetadata":{"orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","shortName":"GitHub_M","dateUpdated":"2026-11-04T21:38:04.613Z"},"descriptions":[{"lang":"en","value":"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."}],"source":{"advisory":"GHSA-m998-r5ww-rqjf","discovery":"UNKNOWN"}}}}