CGI versions before 5.00 for Perl allow HTTP header injection via entity decoding after the newline check in header
Source GCVE Database
Not known to be exploited : upgrade to 5.00 soon.
Data as of 4 Nov 2026, 01:58 UTC
Rated High by Threat Radar's AI analysis · CVSS not yet scored by NVD
Thin evidence
One scorer or none- Patch
- Available – fixed in 5.00
Exploitation evidence
Disclosed: evidence found.
CVE published 3 Nov 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 3 Nov 2026.
What to do
Upgrade CGI (Perl module) to 5.00.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| CGI | Affected
| Fixed in
|
CPANCGIpkg:cpan/CGIOther threats | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
If you cannot patch yet, avoid passing untrusted user input into HTTP header values processed by CGI versions before 5.00 for Perl, especially when autoEscape is off. Validate and sanitize all header-related inputs to prevent injection of encoded newline characters.
Description
CGI versions before 5.00 for Perl have a vulnerability that allows HTTP header injection. This occurs because the header decoding process decodes HTML entities after the newline check, allowing encoded carriage return or line feed characters to reach the response. Additionally, multipart_start and do_push functions do not properly validate header values or types, enabling attackers to inject headers or split HTTP responses when request data is passed into these header values.
References
- nvd.nist.gov/vuln/detail/CVE-2026-120639 (opens in a new tab)
- github.com/leejo/CGI.pm/commit/69955309d371c8093d11cf12e3ddef491537ffad.patch (opens in a new tab)
- github.com/leejo/CGI.pm/commit/7733c2753f4f240012097507cda2b6e87ae46db4.patch (opens in a new tab)
- metacpan.org/release/LEEJO/CGI-4.72/source/lib/CGI.pm (opens in a new tab)
- metacpan.org/release/LEEJO/CGI-5.00/changes (opens in a new tab)