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
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.
Fixes and workarounds
Fix
Upgrade to CGI 5.00 or later.
Source: CNA: CPANSecWorkaround
For deployments that cannot upgrade, strip X-Forwarded-Host at the web server or proxy unless it sets the header itself, and validate Host.
Source: CNA: CPANSecFix
The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches.
Source: CNA: CPANSecAffected products and versions
| Product | Versions | Authority |
|---|---|---|
CGI
cpan |
≥ 0; < 5.00 (affected, custom)
Other versions: unaffected |
CNA: CPANSec |
Version ranges are source assertions. Check the vendor advisory and your installed configuration before determining exposure.
CVSS assessments
No CVSS assessment reported. An unscored record is not a low-severity determination.
Exploit evidence
No exploit evidence in collected sources. This is not proof of no exploitation.
References
- https://metacpan.org/release/LEEJO/CGI-4.72/source/lib/CGI.pmCNA: CPANSec · technical-description
- https://metacpan.org/release/LEEJO/CGI-5.00/changesCNA: CPANSec · release-notes
- https://github.com/leejo/CGI.pm/commit/d76752a5e8dfd365b0fe3a0b9a7da6c054e856af.patchCNA: CPANSec · patch
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