CVE-2026-15603 morgan vulnerable to Log Forging via unescaped Unicode line separators
- Exploited in the wild
- Not known
- Fix
- Available
What is CVE-2026-15603?
CVE-2026-15603 is a medium-severity vulnerability in morgan, published on 28 Aug 2026.
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.
Weakness: CWE-117
Which versions are affected by CVE-2026-15603?
2 open source packages ship an affected version, including morgan. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
morgan npm | All versions | 1.12.0 |
morgan npm | All versions | 1.12.0 |
Products include Morgan Project Morgan.
How do I fix CVE-2026-15603?
Upgrade morgan to 1.12.0 or later.
Is CVE-2026-15603 being exploited?
There is no known exploitation of CVE-2026-15603 in the wild and no public exploit code.
Other vulnerabilities in morgan
Sources
Also known as CLSA-2026-1788988321, CLSA-2026-1790108609, DEBIAN-CVE-2026-15603, GHSA-jxfw-x594-9x9m, MINI-6r4p-p49x-42cq, MINI-vhj5-2rj7-vmfr and 1 more.