CVE intelligence and bounded remediation

CVE-2020-27304 — Civetweb Project Civetweb security vulnerability

Critical CVSS 9.8

The CivetWeb web library does not validate uploaded filepaths when running on an OS other than Windows, when using the built-in HTTP form-based file upload mechanism, via the mg_handle_form_request API. Web applications that use the file upload form handler, and use parts of the user-controlled filename in the output path, are susceptible to directory traversal

Severity
Critical
CVSS
9.8 (3.1)
Published
2021-10-21
CISA KEV
Not currently listed
Ecosystem
windows/system
Weaknesses
CWE-23, CWE-22

Affected products

  • civetweb_project / civetweb
  • siemens / sinec_infrastructure_network_services

Matched remediation archetype

Path traversal, unsafe upload, and file handling

This catalog composition supplies bounded fallback guidance. Explicitly reviewed curated workflows load with the complete record below.

Check exposure

  • Trace untrusted filenames, archive entries, URLs, and path segments into read, write, include, extraction, and upload operations.
  • Identify filesystem roots, mount permissions, symbolic-link behavior, archive handling, and whether uploaded content is web-accessible or executable.
  • Review canonicalization and containment checks across supported operating systems and storage backends.

Remediate safely

  • Generate server-side storage identifiers and resolve paths beneath a fixed root using filesystem-aware containment checks.
  • Reject absolute, parent-relative, alternate-separator, device, link, and archive entries that escape the intended root.
  • Store uploads outside executable or served paths, validate type and size, and use private atomic temporary files.

Authoritative sources

Complete CVE record and remediation plan

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