# CVE-2026-120639: CGI versions before 5.00 for Perl allow HTTP header injection via entity decoding after the newline check in header and unchecked values in multipart_start and do_push

Status: published. Published: 2026-11-03. Updated: 2026-11-03.

CGI versions before 5.00 for Perl allow HTTP header injection via entity decoding after the newline check in header and unchecked values in multipart_start and do_push.

With autoEscape off, header decodes HTML entities in extra header values after its newline check, so an encoded CR or LF reaches the response. multipart_start does not check header values for newlines, and do_push does not check the type it prints in each part.

An application that passes request data into these header values can be made to add headers or split the response.

## Remediation

- fix: Upgrade to CGI 5.00 or later. (source: CNA: CPANSec)
- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: CPANSec) — https://github.com/leejo/CGI.pm/commit/69955309d371c8093d11cf12e3ddef491537ffad.patch
- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: CPANSec) — https://github.com/leejo/CGI.pm/commit/7733c2753f4f240012097507cda2b6e87ae46db4.patch

## Affected products and versions

-  /  (CGI): ≥ 0; < 5.00 (affected, custom). Source: CNA: CPANSec

## Severity and prioritization

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: CWE-113

## 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.pm (CNA: CPANSec; technical-description)

- https://metacpan.org/release/LEEJO/CGI-5.00/changes (CNA: CPANSec; release-notes)

- https://github.com/leejo/CGI.pm/commit/69955309d371c8093d11cf12e3ddef491537ffad.patch (CNA: CPANSec; patch)

- https://github.com/leejo/CGI.pm/commit/7733c2753f4f240012097507cda2b6e87ae46db4.patch (CNA: CPANSec; patch)

## Provenance

- CNA: CPANSec: https://www.cve.org/CVERecord?id=CVE-2026-120639; retrieved 2026-11-04; source updated 2026-11-03

Revision: 95f9594305fa31e860cfce15a7698570a67dbd30f1b19508c91e0e84085a0350

Canonical: https://y2.dev/cve/CVE-2026-120639

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