CGI versions before 5.00 for Perl trust the client X-Forwarded-Host header in url, self_url, virtual_host and virtual_port.

These take the host name and port from the X-Forwarded-Host request header when present, and otherwise from Host, without validating either. The URLs from url and self_url are the default redirect location and the start_html(-base=>1) base href, and the default start_form action when REQUEST_URI is not set.

A client can poison shared caches, and URLs the application stores or sends, with redirects, links and scripts that point at a host it controls.
Advisories

No advisories yet.

Fixes

Solution

Upgrade to CGI 5.00 or later.


Workaround

For deployments that cannot upgrade, strip X-Forwarded-Host at the web server or proxy unless it sets the header itself, and validate Host.

History

Wed, 04 Nov 2026 12:15:00 +0000

Type Values Removed Values Added
References
Metrics threat_severity

None

cvssV3_1

{'score': 6.1, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N'}

threat_severity

Moderate


Wed, 04 Nov 2026 00:00:00 +0000

Type Values Removed Values Added
Description CGI versions before 5.00 for Perl trust the client X-Forwarded-Host header in url, self_url, virtual_host and virtual_port. These take the host name and port from the X-Forwarded-Host request header when present, and otherwise from Host, without validating either. The URLs from url and self_url are the default redirect location and the start_html(-base=>1) base href, and the default start_form action when REQUEST_URI is not set. A client can poison shared caches, and URLs the application stores or sends, with redirects, links and scripts that point at a host it controls.
Title CGI versions before 5.00 for Perl trust the client X-Forwarded-Host header in url, self_url, virtual_host and virtual_port
Weaknesses CWE-348
CWE-601
References

Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: CPANSec

Published:

Updated: 2026-11-03T23:40:04.604Z

Reserved: 2026-11-02T17:40:07.895Z

Link: CVE-2026-120633

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-11-04T00:17:24.450

Modified: 2026-11-04T00:17:24.450

Link: CVE-2026-120633

cve-icon Redhat

Severity : Moderate

Publid Date: 2026-11-03T23:40:04Z

Links: CVE-2026-120633 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-11-04T08:45:11Z

Weaknesses