CVE-2026-5078Medium· 5.3▾ Sunlitmorgan vulnerable to Log Forging via unneutralized control characters in :remote-user
▾ Sunlit zone — Low / medium · no exploitation signal
impact 29.2 · likelihood 0.1 · exploitation 0
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Exploit-prediction probability, daily snapshots since Aug 2.
Disclosure to exploitation, from the record and what we observed since indexing it.
Disclosed via GHSA
0.3%
0.3% → 0.4%
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.
Users should upgrade to version 1.11.0.
Use a custom format string that does not include :remote-user.
morgan >= 1.2.0, <= 1.10.1Upgrade to a patched release:
morgan 1.11.0Connected by shared product, vendor, weakness, or advisory.
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