CVE-2026-120633

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

Published Nov 3, 2026 CVSS 3.1 · 6.1 Medium EPSS < 1% KEV · Not listed
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.

Remediation

Vendor Solution

Upgrade to CGI 5.00 or later.


Vendor 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.

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

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

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

Subscriptions

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Weaknesses

Sources

Status
PUBLISHED
Assigner
CPANSec
Published
Updated
Nov 9, 2026, 6:53 PM
Reserved
Nov 2, 2026, 5:40 PM
Status
Deferred
Published
Nov 4, 2026, 12:17 AM
Modified
Nov 9, 2026, 7:16 PM
Severity
Moderate
Public date
Nov 3, 2026, 11:40 PM