CVE-2026-5078 (GCVE-0-2026-5078)

Vulnerability from cvelistv5 – Published: 2026-06-03 05:56 – Updated: 2026-06-03 13:19
VLAI
Title
morgan vulnerable to Log Forging via unneutralized control characters in :remote-user
Summary
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.
Severity
5.3 (Medium)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
SSVC
Exploitation: none Automatable: yes Technical Impact: partial
CISA Coordinator (v2.0.3)
CWE
  • CWE-117 - Improper Output Neutralization for Logs
Assigner
References
Impacted products
Vendor Product Version
morgan morgan Affected: 1.2.0 , ≤ 1.10.1 (semver)
Unaffected: 1.11.0 (semver)
Create a notification for this product.
Credits
Yuki Matsuhashi Ulises Gascón Jon Church
Show details on NVD website
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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

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  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
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