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Vulnerability · Published Nov 3, 2026 · Assigned by CPANSec

CVE-2026-120639CGI 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

Unrated

In plain English

A security flaw in CGI. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 13% of all known vulnerabilities).

Severity (CVSS )–Not rated
Exploit odds (30 days)0.2%top 86.5% of all CVEs
Exploited in the wildNo reportsnot in CISA KEV
Attack toolingNoneno public tooling known

Official description

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.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Debian:12libcgi-pm-perlno fix listedDEBIAN-CVE-2026-120639
Debian:13libcgi-pm-perlno fix listedDEBIAN-CVE-2026-120639
Debian:14libcgi-pm-perlno fix listedDEBIAN-CVE-2026-120639
Ubuntu:22.04:LTSlibcgi-pm-perlno fix listedUBUNTU-CVE-2026-120639
Ubuntu:24.04:LTSlibcgi-pm-perlno fix listedUBUNTU-CVE-2026-120639
Ubuntu:26.04:LTSlibcgi-pm-perlno fix listedUBUNTU-CVE-2026-120639
Ubuntu:26.10libcgi-pm-perlno fix listedUBUNTU-CVE-2026-120639

Affected products (as reported)

VendorProductVersions
CGI 0 – before 5.00

Weakness: CWE-113

References