# CVE-2026-120646: CGI Perl denial of service via symbolic reference in uploadInfo

Source: https://junglewise.ai/threats/cve-2026-120646-cgi-versions-from-4-71-before-5-00-for-perl-allow-denial-of  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-11-04. Updated: 2026-11-04  
License: CC BY 4.0 with a link back

CVE-2026-120646 · Severity: info · Published 2026-11-04

CGI.pm is a widely-used Perl library for building web applications. A denial-of-service flaw allows an attacker to crash a web application by sending a specially crafted request parameter (such as ?upload=0) that causes the application to unexpectedly terminate. The vulnerability affects CGI versions 4.71 through 4.99.

Vendors: [Perl](https://junglewise.ai/threats/vendors/perl).

## Quick answers

**Is CVE-2026-120646 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-120646 being exploited in the wild.

**How severe is CVE-2026-120646?** Informational severity, published 4 November 2026.

**Which products and versions are affected?** Perl CGI.pm 4.71 before 5.00.

**Is there a fix for CVE-2026-120646?** Yes: fixed in CGI.pm 5.00 and later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-120646 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-120646?** Check whether you run Perl CGI.pm 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.pm 5.00 and later

## Technical details

The uploadInfo() method in CGI.pm dereferences its argument without type checking, treating plain strings as symbolic references. When a parameter value matches a defined global variable name (e.g., "0" for $0, or "VERSION"), the code attempts to call a method on the string, causing an exception. A remote attacker can exploit this via query parameters to trigger application crashes. The fix checks that the argument is a reference with a filename method before proceeding.

## Affected products

- Perl CGI.pm 4.71 before 5.00

## Timeline

- 2026-11-04: disclosed
- 2026-11-02: patched: Fix committed to GitHub

## References

- [https://cpan.org/modules](https://cpan.org/modules)
- [https://github.com/leejo/CGI.pm/commit/a14a7decfdc18f2daf436d30df9b543e3f0f8da3.patch](https://github.com/leejo/CGI.pm/commit/a14a7decfdc18f2daf436d30df9b543e3f0f8da3.patch)

## Related threats

- [CGI.pm parameter injection via reserved param names](https://junglewise.ai/threats/cve-2026-120640-cgi-versions-before-5-00-for-perl-allow-the-postdata-putdata)