{"id":"CVE-2026-5078","aliases":["GHSA-4vj7-5mj6-jm8m"],"url":"https://o3.security/vulnerability/CVE-2026-5078","summary":"morgan vulnerable to Log Forging via unneutralized control characters in :remote-user","details":"Impact: The morgan logging middleware's :remote-user token extracts the Basic auth username from the Authorization request header and writes it to the log stream without neutralizing control characters. An unauthenticated attacker can send a crafted Authorization Basic header containing CR or LF bytes to inject forged log lines, breaking the one-request-per-line structure of access logs and enabling log forgery against downstream log consumers. The built-in combined, common, default, and short formats are affected, as well as any custom format that references :remote-user. Affected versions: morgan 1.2.0 through 1.10.1. Patches: upgrade to morgan 1.11.0, which neutralizes control characters in the :remote-user token output. Workarounds: use a custom format string that does not include :remote-user.","published":"2026-06-03T05:56:49.512Z","modified":"2026-08-12T03:51:47.275106532Z","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":{"score":0.00332,"percentile":0.25971,"asOf":"2026-09-08"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"npm","name":"morgan","fixedVersion":"1.11.0"}],"fix":null,"references":[{"type":"ADVISORY","url":"https://cna.openjsf.org/security-advisories.html"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/5xxx/CVE-2026-5078.json"},{"type":"ADVISORY","url":"https://github.com/expressjs/morgan/security/advisories/GHSA-4vj7-5mj6-jm8m"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-5078"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:47.275106532Z"}}