Vulnerability · Published Aug 28, 2026 · Assigned by openjs
CVE-2026-15603morgan vulnerable to Log Forging via unescaped Unicode line separators
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 0.4% (higher than 34% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
morgan is an HTTP request logger middleware for Node.js. In versions prior to 1.12.0, the internal helper that escapes log token values did not neutralize the Unicode line separator characters U+0085 (Next Line), U+2028 (Line Separator), and U+2029 (Paragraph Separator). An unauthenticated remote client can place these characters in an attacker-controlled log token, for example a Basic auth username surfaced through the remote-user token, so that Unicode-aware downstream log processing splits 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, which only addressed ASCII control characters. The issue is fixed in morgan 1.12.0, which extends the escaping set to cover these Unicode line separators. Upgrade to morgan 1.12.0 to remediate.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | node-morgan | no fix listed | DEBIAN-CVE-2026-15603 |
| Debian:13 | node-morgan | no fix listed | DEBIAN-CVE-2026-15603 |
| Debian:14 | node-morgan | 1.12.0+~1.9.10-1 | DEBIAN-CVE-2026-15603 |
| Ubuntu:22.04:LTS | node-morgan | no fix listed | UBUNTU-CVE-2026-15603 |
| Ubuntu:24.04:LTS | node-morgan | no fix listed | UBUNTU-CVE-2026-15603 |
| Ubuntu:26.04:LTS | node-morgan | no fix listed | UBUNTU-CVE-2026-15603 |
| Ubuntu:26.10 | node-morgan | no fix listed | UBUNTU-CVE-2026-15603 |
| npm | morgan | 1.12.0 | GHSA-jxfw-x594-9x9m |
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