Is CVE-2026-120633 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-120633 being exploited in the wild.

How severe is CVE-2026-120633?

Informational severity, published 4 November 2026.

How is CVE-2026-120633 attacked?

It is attacked over the network, in a software library.

Am I affected by CVE-2026-120633?

Check whether you run Perl CGI at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-120633: CGI for Perl improper validation of X-Forwarded-Host

CVE-2026-120633 · Severity: info · Published 2026-11-04

CGI is a foundational Perl module that web applications use to handle HTTP requests and generate responses. Versions before 5.00 trust the X-Forwarded-Host header sent by clients, allowing attackers to inject arbitrary hostnames into generated URLs. This enables cache poisoning attacks, malicious redirects, and credential harvesting when applications store or send these URLs.

Technologies: Perl CGI. Vendors: Perl.

Quick answers

Is CVE-2026-120633 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-120633 being exploited in the wild.
How severe is CVE-2026-120633?: Informational severity, published 4 November 2026.
Which products and versions are affected?: Perl CGI before 5.00.
Is there a fix for CVE-2026-120633?: Yes: fixed in CGI 5.00. Until then: Set $CGI::TRUST_X_FORWARDED_HOST = 1 to restore pre-5.00 behavior only if all requests come through a reverse proxy that sets the header; alternatively, configure the reverse proxy or web server to pass the correct Host header or SERVER_NAME to the application. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-120633 attacked?: It is attacked over the network, in a software library.
Am I affected by CVE-2026-120633?: Check whether you run Perl CGI at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

Fixed in: CGI 5.00

Set $CGI::TRUST_X_FORWARDED_HOST = 1 to restore pre-5.00 behavior only if all requests come through a reverse proxy that sets the header; alternatively, configure the reverse proxy or web server to pass the correct Host header or SERVER_NAME to the application.

Technical details

CGI versions before 5.00 use the client-supplied X-Forwarded-Host header without validation in url(), self_url(), virtual_host(), and virtual_port() functions, defaulting to the Host header only if X-Forwarded-Host is absent. An unauthenticated network attacker can set this header to control the hostname in generated redirects, HTML base hrefs, and form actions, leading to open redirects and shared cache poisoning. The fix validates the Host header against a syntactic whitelist and disables X-Forwarded-Host by default, requiring applications behind proxies to be reconfigured.

Affected products

Perl CGI before 5.00

Timeline

2026-11-04: disclosed
2026-11-02: patched: patch committed

References

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