GitHub Advisoryadvisory · npm

GHSA-4vj7-5mj6-jm8m morgan vulnerable to Log Forging via unneutralized control characters in :remote-user

MEDIUM Published 2026-07-10 Modified 2026-07-10 Official page ↗
Aliases
CVE-2026-5078
Ecosystem
npm
Packages
morgan
Severity
Moderate
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
Weaknesses
CWE-117
Reviewed
2026-07-10

Affected packages

• npm morgan: >= 1.2.0, < 1.11.0 → fixed in 1.11.0

Description

Impact Morgan's `:remote-user` token extracts the Basic auth username from the `Authorization` header and writes it to the log stream without neutralizing control characters. An attacker can send a crafted `Authorization: Basic` header containing CR/LF characters to inject forged log lines, corrupting the one-request-per-line structure of access logs. The built-in `combined`, `common`, `default`, and `short` formats are affected, as well as any custom format that includes `:remote-user`. Patches Users should upgrade to version 1.11.0. Workarounds Use a custom format string that does not include `:remote-user`.

Related

Alias · CVE (1)

  • CVE-2026-5078 Impact: The morgan logging middleware's :remote-user token extracts the Basic auth username from the Authorization request header and… vulnerability

Weakness · CWE (1)

  • CWE-117 Improper Output Neutralization for Logs weakness

References