Improper Output Neutralization for Logs Affecting morgan package, versions <1.12.0
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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- published30 Aug 2026
- disclosed28 Aug 2026
- creditM. Fazri Nizar, iaohkut
Introduced: 28 Aug 2026
NewCVE-2026-15603 (opens in a new tab)How to fix?
Upgrade morgan to version 1.12.0 or higher.
Overview
morgan is a HTTP request logger middleware for node.js.
Affected versions of this package are vulnerable to Improper Output Neutralization for Logs in its format-token expansion, which does not neutralize the Unicode line separators U+0085 (NEL), U+2028 (LINE SEPARATOR), and U+2029 (PARAGRAPH SEPARATOR) in logged fields such as :url, :user-agent, :referrer, :req[header], and :remote-user, unlike the earlier fix that escaped C0 control characters. An attacker can forge additional log records by sending ordinary HTTP request headers or a request URL containing these characters, which Unicode-aware downstream log processors interpret as line breaks and split into separate entries. Exploitation requires the downstream log analysis tooling to treat these code points as record separators, and all built-in formats (combined, common, default, and short) are affected.
Note: This is a bypass of the fix for the vulnerability described in CVE-2026-5078.