CVE-2026-15603

MEDIUMPre-NVD 5.35.3—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 5.3 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.2%, top 85% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
5.3EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 5.3Exploit: None knownExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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.

CVSS v3
5.3
EG Score
5.3(medium)
EG Risk
39(Track)
EG Risk 39/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity53% × 45%
Exploitation0% × 40%
Automatability100% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
15%
KEV
Not listed

Published

August 28, 2026

Last Modified

August 31, 2026

Advisory Details (2)

Auto-updated Aug 28, 2026
Patch available. Sources: github.
generic

Security Advisories | OpenJS Foundation CVE Numbering Authority

https://cna.openjsf.org/security-advisories.html
github Patch Available

morgan vulnerable to Log Forging via unescaped Unicode line separators · Advisory · expressjs/morgan · GitHub

https://github.com/expressjs/morgan/security/advisories/GHSA-jxfw-x594-9x9m

Vendor Advisories for CVE-2026-15603(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(3 across 3 ecosystems)
Debian:12(1)
PackageVulnerable rangeFixed inDependents
node-morgan1.10.0+~1.9.3-1, 1.10.1+~1.9.10-1, 1.12.0+~1.9.10-1——
Debian:13(1)
PackageVulnerable rangeFixed inDependents
node-morgan1.10.0+~1.9.3-1, 1.10.1+~1.9.10-1, 1.12.0+~1.9.10-1——
Debian:14(1)
PackageVulnerable rangeFixed inDependents
node-morgan1.10.0+~1.9.3-1, 1.10.1+~1.9.10-11.12.0+~1.9.10-1—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 11× in last 7d / 37× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-09-19 00:14 UTCEG score recompute
  2. 2026-09-18 19:27 UTCEPSS rescore
  3. 2026-09-18 00:16 UTCEG score recompute
  4. 2026-09-17 00:18 UTCEG score recompute
  5. 2026-09-16 14:07 UTCEPSS rescore
  6. 2026-09-16 05:14 UTCEPSS rescore
  7. 2026-09-16 00:19 UTCEG score recompute
  8. 2026-09-14 00:22 UTCEG score recompute
  9. 2026-09-13 16:46 UTCEPSS rescore
  10. 2026-09-13 00:24 UTCEG score recompute
  11. 2026-09-12 15:00 UTCEPSS rescore
  12. 2026-09-12 00:25 UTCEG score recompute
  13. 2026-09-11 14:52 UTCEPSS rescore
  14. 2026-09-11 09:36 UTCEPSS rescore
  15. 2026-09-11 00:27 UTCEG score recompute
  16. 2026-09-10 09:34 UTCEPSS rescore
  17. 2026-09-09 00:29 UTCEG score recompute
  18. 2026-09-08 22:00 UTCEPSS rescore
  19. 2026-09-07 20:28 UTCEG score recompute
  20. 2026-09-07 16:01 UTCEPSS rescore
  21. 2026-09-06 20:30 UTCEG score recompute
  22. 2026-09-06 13:47 UTCEPSS rescore
  23. 2026-09-05 20:31 UTCEG score recompute
  24. 2026-09-04 20:33 UTCEG score recompute
  25. 2026-09-02 20:24 UTCEG score recompute
Show 12 more
  1. 2026-09-02 14:11 UTCEPSS rescore
  2. 2026-09-01 17:24 UTCEG score recompute
  3. 2026-09-01 13:53 UTCEPSS rescore
  4. 2026-09-01 04:39 UTCEPSS rescore
  5. 2026-08-30 20:19 UTCEG score recompute
  6. 2026-08-30 19:17 UTCEPSS rescore
  7. 2026-08-30 01:22 UTCEPSS rescore
  8. 2026-08-28 19:58 UTCEG score recompute
  9. 2026-08-28 19:44 UTCEG score recompute
  10. 2026-08-28 16:33 UTCEG score recompute
  11. 2026-08-28 15:29 UTCEG score recompute
  12. 2026-08-28 15:25 UTCMITRE cvelistV5first tracked

Frequently asked(5)

What is CVE-2026-15603?
CVE-2026-15603 is a medium vulnerability published on August 28, 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…
When was CVE-2026-15603 disclosed?
CVE-2026-15603 was first published in the National Vulnerability Database on August 28, 2026, with the most recent update on August 31, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-15603 actively exploited?
CVE-2026-15603 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 85.2% of all scored CVEs.
What is the CVSS score of CVE-2026-15603?
CVE-2026-15603 has a CVSS v3 base score of 5.3 (NVD).
How do I remediate CVE-2026-15603?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-15603, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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