CVE-2026-5078
morgan vulnerable to Log Forging via unneutralized control characters in :remote-user
- State
- Published
- Severity
- 5.3 Medium
- Published
- Jun 3, 2026
- Updated
- Jun 3, 2026
- Reserved
- Mar 28, 2026
Description
Impact: The morgan logging middleware's :remote-user token extracts the Basic auth username from the Authorization request header and writes it to the log stream without neutralizing control characters. An unauthenticated attacker can send a crafted Authorization Basic header containing CR or LF bytes to inject forged log lines, breaking the one-request-per-line structure of access logs and enabling log forgery against downstream log consumers. The built-in combined, common, default, and short formats are affected, as well as any custom format that references :remote-user. Affected versions: morgan 1.2.0 through 1.10.1. Patches: upgrade to morgan 1.11.0, which neutralizes control characters in the :remote-user token output. Workarounds: use a custom format string that does not include :remote-user.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 3.1 | 5.3 Medium | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N | openjs |
Weaknesses
- CWE-117 Improper Output Neutralization for Logs
Affected Products
| Product | Versions |
|---|---|
morganmorgan |
|
References
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