morgan vulnerabilities

An attacker can use the format parameter to inject arbitrary commands in the npm package morgan < 1.9.1.

morgan is an HTTP request logger middleware for Node.js. In versions before 1.12.1, its escapeLogField() function does not escape the double quote character, which delimits the quoted fields of the Apache combined log format that morgan emits. An unauthenticated remote attacker who controls a value written to a quoted field, such as the User-Agent or Referer header, can include a double quote to close that field early, so a log consumer that parses the log by field position reads attacker-supplied text as the following field.

Morgan, an HTTP request logger middleware for Node.js, in versions prior to 1.12.0 did not neutralize the Unicode line separator characters U+0085, U+2028, and U+2029 in log token values. An unauthenticated remote client can place these characters in an attacker-controlled log token, such as a Basic auth username, causing downstream log processing to split 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. The issue is fixed in morgan 1.12.0.

Morgan, a popular Node.js logging middleware, has a log forgery vulnerability. The :remote-user token outputs the Basic Auth username without neutralizing control characters, allowing an attacker to inject forged log lines.