5.3

CVE-2026-15603: morgan vulnerable to Log Forging via unescaped Unicode line separators

Analyzed
AliasesUBUNTU-CVE-2026-15603DEBIAN-CVE-2026-15603GHSA-jxfw-x594-9x9m
Published 28-08-2026Last modified 28-08-2026

Vulnerability summary

CVE-2026-15603 is a medium (CVSS 5.3) Improper Output Neutralization for Logs vulnerability in morgan_project morgan. EPSS estimates a 0.40% chance of exploitation in the next 30 days, higher than 33.9% of scored vulnerabilities.

Priority
Routine

Not severe (CVSS 5.3, network access); no exploitation reported by the 5 checked sources

Source freshness unavailable

How is this decided?
CVSS score
5.3/10
010
Medium · v3.1 (CVE.org)
EPSS score
0.40%
0%100%
Low · +0.10 pp in 30 days
KEVNot listedNot listed by any tracked catalog.
RansomwareNot flaggedNo ransomware use recorded.
Public exploits0No public exploits recorded

Timeline

  1. 28-08-2026
    PublishedVulnerability first disclosed.
  2. 28-08-2026
    Last modifiedVulnerability information updated.

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.

CVSS metrics

6 scores · 6 sources · 1 version

EPSS trend

Probability

0.40%

Chance of exploitation in the next 30 days

Percentile

34%

Versus all other CVEs

30-day change

Increase +0.10 pp

From 0.29% on 04-10-2026

04-10-202603-11-2026

Known exploited

Compare KEV catalogs
CISA KEV

Not in the CISA KEV catalog.

ENISA CNW

Not in the ENISA CNW catalog.

CIRCL

Not in the CIRCL catalog.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Version check

Known conditions: network-reachable, no authentication, no user interaction (CVSS vector). Other conditions: not stated in public data.

Chainguard3 products
  • azurite< 3.36.0-r5
  • wazuh-dashboard-security-plugin< 4.14.7-r19
  • wazuh-dashboard-security-plugin-fips< 4.14.7-r19
Debian1 product
  • node-morganAll versions (No fix recorded) | < 1.12.0+~1.9.10-1
Morgan1 product
Morgan_project1 product
Npm1 product
  • morgan< 1.12.0
Ubuntu1 product
  • node-morganAll versions (No fix recorded)

6 vendors · 8 products

References

10 links