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CVE-2026-15603

5.3 · MEDIUM

morgan is an HTTP request logger middleware for Node.js.

Published Aug 28, 2026CWE-117EPSS 0.29%

Overview

CVE-2026-15603 is a medium-severity vulnerability. It was published on August 28, 2026 and has a CVSS 3.1 base score of 5.3 (MEDIUM).

This vulnerability has a CVSS 3.1 base score of 5.3, rated MEDIUM. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical 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.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

Refcna.openjsf.org/security-advisories.htmlGitHubgithub.com/expressjs/morgan/security/advisories/GHSA-jxfw-x594-9x9m

How CyberStrike helps

Frequently asked questions

What is CVE-2026-15603?

CVE-2026-15603 is a medium-severity vulnerability. It was published on August 28, 2026 and has a CVSS 3.1 base score of 5.3 (MEDIUM).

How severe is CVE-2026-15603?

This vulnerability has a CVSS 3.1 base score of 5.3, rated MEDIUM. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2026-15603?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-15603?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-15603 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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