All vulnerabilities
CVE-2026-87859GHSA-9f6g-j8ch-79g4

morgan vulnerable to Log Injection via unescaped double quote in quoted log fields

morgan morgannpmLibraries & packages
Open in ThreatlineRecord JSON
CVSS
5.3Medium
ExploitationNo known exploitationNot in CISA KEV, which does not prove it is unexploitedCISA KEV
Exploit odds (EPSS)0.41%Chance of exploitation activity in the next 30 days, higher than 34% of CVEs. Scored 23 Oct 2026FIRST EPSS
Fixed in1.12.1Fixed versionGitHub
Published11 Sep 2026Updated 28 Sep 2026CVE List

What fixes it

A fixed version on one release line is not the upgrade target for every line. Check your exact version and any vendor backports.

Description

Impact

Morgan writes attacker-controlled request data to the access log. Its escaping (added in 1.11.0 and 1.12.0) neutralizes control characters, the Unicode line separators, and backslash, but not the double quote (0x22), which is the field delimiter of the Apache combined log format morgan emits. An attacker who controls a quoted field (:user-agent, :referrer, the request URL, or the Basic auth :remote-user) can inject a double quote to close the field early and forge additional fields in the log record. The combined, common, and default formats, and any custom format that quotes a token, are affected. This is an incomplete fix of CVE-2026-5078 and CVE-2026-15603.

Patches

Users should upgrade to version 1.12.1.

Workarounds

Update to version 1.12.1.

Text from GitHub Advisory Database

Affected versions 4

  • morgan, npm< 1.12.1GitHub
  • morganaffected: all versions before 1.12.1CVE List
  • morganunaffected: 1.12.1CVE List
  • morgan, npmfrom first release, fixed in 1.12.1OSV

References 6