HTTP header injection in Perl CGI module through unchecked values
Key facts
- Attack vector
- —
- Privileges required
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- User interaction
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- Attack complexity
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- Impact type
- —
- Confidentiality · integrity · availability
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- Fix status
- Partial Red Hat: 4 without a fix
No CVSS vector from any source. Fix status from CNA and Red Hat.
Summary
CGI for Perl versions before 5.00 allow HTTP header injection. With autoEscape off, header decodes HTML entities in extra header values after its newline check, so encoded CR or LF characters reach the response (CWE-113). 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 lets an attacker add headers or split the response.
Written with Claude Haiku 5.5 from the sources below · 2026-11-04
Description from the CNA
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.
Why it matters now
SSVC decision points
Not available: CISA has not published SSVC decision points for this record.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| — | CGI | before 5.00 | 5.00 | Patch available | CNA |
- CGI Vendor— Affected before 5.00 Fixed in 5.00 Patch available CNA
Remediation
Upgrade CGI for Perl to version 5.00 or later. Red Hat lists Enterprise Linux 7, 8, 9 and 10 as affected, and the sources list no fixed version for them.
Written with Claude Haiku 5.5 from the sources below · 2026-11-04
- Fix · CNA CGI Fixed in 5.00
Vendor assessments
Red Hat
Red Hat rating: Moderate. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat Enterprise Linux 10 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 7 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 8 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 9 | Affected | No fix yet: Fix deferred |
Timeline
- 2026-11-03 Threatist record created from CVE-2026-120639
- 2026-11-04 Affected versions changed · Red Hat
- 2026-11-04 CVSS score added · Red Hat
- 2026-11-04 Alias added: GHSA-mxvj-3jfg-j4p6
References
Sources
- CVE-2026-120639 · CVE Program
- CVE-2026-120639 · NVD
- FIRST EPSS
- GHSA-mxvj-3jfg-j4p6 · GitHub Advisory Database · CC BY 4.0
- CVE-2026-120639 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences