Quick answers
- Is CVE-2026-120637 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-120637 being exploited in the wild.
- How severe is CVE-2026-120637?
- Informational severity, published 4 November 2026.
- Which products and versions are affected?
- Perl CGI before 5.00.
- Is there a fix for CVE-2026-120637?
- Yes: fixed in CGI 5.00. Until then: Upgrade to CGI 5.00 or later. As an interim measure, disable the $DEBUG flag by setting $CGI::DEBUG = 0 before creating CGI objects in your application. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-120637 attacked?
- It is attacked over the network, in a software library.
- Am I affected by CVE-2026-120637?
- 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
Upgrade to CGI 5.00 or later. As an interim measure, disable the $DEBUG flag by setting $CGI::DEBUG = 0 before creating CGI objects in your application.
Technical details
The vulnerability exists in CGI.pm versions before 5.00, where the offline debugging mode (controlled by $DEBUG, enabled by default) incorrectly activates for any unrecognized REQUEST_METHOD instead of only when there is no HTTP request at all. An attacker can send a request with a non-standard REQUEST_METHOD (e.g., OPTIONS, PROPFIND, lowercase "post") to a CGI application, causing the process command-line arguments to be parsed as CGI parameters and path_info. The fix restricts offline mode activation to cases where REQUEST_METHOD is undefined and the process is not running under any CGI server (CGI, FastCGI, or mod_perl).
Affected products
- Perl CGI before 5.00
Timeline
- 2026-11-04: disclosed
- 2026-11-02: patched: Fix committed to GitHub