CVE-2021-33621

Severity: high (CVSS 8.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 2.5% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2022-11-18 · updated 2026-06-17
Weakness: CWE-74

Description

The cgi gem before 0.1.0.2, 0.2.x before 0.2.2, and 0.3.x before 0.3.5 for Ruby allows HTTP response splitting. This is relevant to applications that use untrusted user input either to generate an HTTP response or to create a CGI::Cookie object.

Affected products

Fedoraproject Fedora: 35, 36, 37
ruby-lang CGI: before 0.1.0.2; from 0.2.0 before 0.2.2; from 0.3.0 before 0.3.5 — fixed in 0.1.0.2, 0.2.2, 0.3.5
Ruby: from 2.7.0 before 2.7.7; from 3.0.0 before 3.0.5; from 3.1.0 before 3.1.3 — fixed in 2.7.7, 3.0.5, 3.1.3

How to fix

Upgrade to a fixed version: ruby-lang CGI 0.1.0.2, 0.2.2, 0.3.5; Ruby 2.7.7, 3.0.5, 3.1.3. Check the vendor advisory for mitigations.

References

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