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Vulnerability record · CVE-2020-27304 · published 21 October 2021

CVE-2020-27304: Civetweb project civetweb relative path traversal vulnerability

CCivetweb Project · Civetweb

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

9.8 CVSS 3.1 Critical EPSS 3.2% · top 12.2% CWE-23 · Relative path traversalCWE-22 · Path traversal
9.8CVSS 3.1 base score, v2 7.5
3.2%EPSS exploitation probability, 30 days
NoNot in CISA KEV
2Affected product versions listed by NVD
8References, 2 tagged exploit
17 Jun 2026Last modified by NVD

Description

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

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

2 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://cert-portal.siemens.com/productcert/pdf/ssa-222547.pdf
https://cert-portal.siemens.com/productcert/pdf/ssa-389290.pdf PatchThird Party Advisory
https://groups.google.com/g/civetweb/c/yPBxNXdGgJQ Mailing ListThird Party Advisory
https://jfrog.com/blog/cve-2020-27304-rce-via-directory-traversal-in-civetweb-http-server/ ExploitThird Party Advisory
https://cert-portal.siemens.com/productcert/pdf/ssa-222547.pdf
https://cert-portal.siemens.com/productcert/pdf/ssa-389290.pdf PatchThird Party Advisory
https://groups.google.com/g/civetweb/c/yPBxNXdGgJQ Mailing ListThird Party Advisory
https://jfrog.com/blog/cve-2020-27304-rce-via-directory-traversal-in-civetweb-http-server/ ExploitThird Party Advisory

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Source: NIST National Vulnerability Database (record CVE-2020-27304), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.