expressjs Morgan up to 1.11.x neutralization for logs

Summaryinfo

A vulnerability has been found in expressjs Morgan up to 1.11.x and classified as problematic. This impacts an unknown function. Performing a manipulation results in neutralization for logs. This vulnerability is known as CVE-2026-15603. Remote exploitation of the attack is possible. No exploit is available.

Detailsinfo

A vulnerability was found in expressjs Morgan up to 1.11.x. It has been classified as problematic. This affects an unknown part. The manipulation with an unknown input leads to a neutralization for logs vulnerability. CWE is classifying the issue as CWE-117. The product does not neutralize or incorrectly neutralizes output that is written to logs. This is going to have an impact on integrity. The summary by CVE is:

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.

It is possible to read the advisory at github.com. This vulnerability is uniquely identified as CVE-2026-15603 since 07/13/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. The technical details are unknown and an exploit is not publicly available.

Upgrading to version 1.12.0 eliminates this vulnerability.

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Productinfo

Vendor

• expressjs

Name

• Morgan

Version

• 1.0
• 1.1
• 1.2
• 1.3
• 1.4
• 1.5
• 1.6
• 1.7
• 1.8
• 1.9
• 1.10
• 1.11

Website

• Product: https://github.com/expressjs/morgan/

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