{"id":"CVE-2026-15603","aliases":["GHSA-jxfw-x594-9x9m"],"url":"https://o3.security/vulnerability/CVE-2026-15603","summary":"morgan vulnerable to Log Forging via unescaped Unicode line separators","details":"morgan is an HTTP request logger middleware for Node.js. In versions prior to 1.12.0, the internal helper that escapes log token values did not neutralize the Unicode line separator characters U+0085 (Next Line), U+2028 (Line Separator), and U+2029 (Paragraph Separator). An unauthenticated remote client can place these characters in an attacker-controlled log token, for example a Basic auth username surfaced through the remote-user token, so that Unicode-aware downstream log processing splits a single request log into multiple logical records. This is a log forging issue (CWE-117) and an incomplete-fix follow-up to CVE-2026-5078, which only addressed ASCII control characters. The issue is fixed in morgan 1.12.0, which extends the escaping set to cover these Unicode line separators. Upgrade to morgan 1.12.0 to remediate.","published":"2026-08-28T13:41:49.521Z","modified":"2026-09-03T03:47:48.634427106Z","cvss":{"score":5.3,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N"},"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[{"ecosystem":"npm","name":"morgan","fixedVersion":"1.12.0"}],"fix":null,"references":[{"type":"ADVISORY","url":"https://cna.openjsf.org/security-advisories.html"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/15xxx/CVE-2026-15603.json"},{"type":"ADVISORY","url":"https://github.com/expressjs/morgan/security/advisories/GHSA-jxfw-x594-9x9m"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-15603"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-09-03T03:47:48.634427106Z"}}