CVE-2026-15603 PUBLISHED

morgan vulnerable to Log Forging via unescaped Unicode line separators

Assigner: openjs
Reserved: 13.07.2026 Published: 28.08.2026 Updated: 28.08.2026

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.

Metrics

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
CVSS Score: 5.3

Product Status

Vendor morgan
Product morgan
Versions Default: unaffected
  • affected from 0 to 1.12.0 (excl.)

Credits

  • mfazrinizar reporter
  • UlisesGascon remediation reviewer
  • jonchurch remediation reviewer
  • bjohansebas remediation developer
  • iaohkut-from-NightWolf-Team reporter

References

Problem Types

  • CWE-117: Improper Output Neutralization for Logs CWE