Vulnerability · Published Jun 3, 2026 · Assigned by openjs
CVE-2026-5078morgan vulnerable to Log Forging via unneutralized control characters in :remote-user
Medium 5.3
In plain English
A medium-severity security flaw in morgan from morgan. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 27% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | node-morgan | no fix listed | DEBIAN-CVE-2026-5078 |
| Debian:13 | node-morgan | no fix listed | DEBIAN-CVE-2026-5078 |
| Debian:14 | node-morgan | 1.12.0+~1.9.10-1 | DEBIAN-CVE-2026-5078 |
| Ubuntu:22.04:LTS | node-morgan | no fix listed | UBUNTU-CVE-2026-5078 |
| Ubuntu:24.04:LTS | node-morgan | no fix listed | UBUNTU-CVE-2026-5078 |
| Ubuntu:25.10 | node-morgan | no fix listed | UBUNTU-CVE-2026-5078 |
| Ubuntu:26.04:LTS | node-morgan | no fix listed | UBUNTU-CVE-2026-5078 |
| Ubuntu:26.10 | node-morgan | no fix listed | UBUNTU-CVE-2026-5078 |
| npm | morgan | 1.11.0 | GHSA-4vj7-5mj6-jm8m |
Affected products (as reported)
Weakness: CWE-117 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N