morgan vulnerable to Log Forging via unneutralized control characters in :remote-user
Impact
Morgan's :remote-user token extracts the Basic auth username from the Authorization header and writes it to the log stream without neutralizing control characters. An attacker can send a crafted Authorization: Basic header containing CR/LF characters to inject forged log lines, corrupting the one-request-per-line structure of access logs.
The built-in combined, common, default, and short formats are affected, as well as any custom format that includes :remote-user.
Patches
Users should upgrade to version 1.11.0.
Workarounds
Use a custom format string that does not include :remote-user.
Affected software
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| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| npm package | morgan | >= 1.2.0, < 1.11.0 | 1.11.0 |
References
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N- Weakness (CWE)
CWE-117- Platform
- npm
- Package
morgan- Disclosed
- 10.07.2026
- Updated
- 11.10.2026 10:22
Sources and licenses
OSV / GitHub Advisory Database - GHSA-4vj7-5mj6-jm8m - CC BY 4.0
Vulnerability history: morgan
All published vulnerabilities of this package (npm package), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 4
- First → latest
- 03.2019 09.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- Critical 1
- Medium 3
Disclosures per year
- 2019: 1
- 2020: 0
- 2021: 0
- 2022: 0
- 2023: 0
- 2024: 0
- 2025: 0
- 2026: 3
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morgan vulnerable to Log Forging via unneutralized control characters in :remote-user this entry
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