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HIGH

CVE-2021-33621

CVSS v3

8.8

HIGH

EPSS Score

2.4 %

exploit probability, as of 2026-10-19

CISA KEV

No

known exploited

Exploitation

—

SSVC status

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Affected and fixed versions

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • cgiRubyGemsall versions · fixed in 0.1.0.2
  • rubyBitnamifrom 2.7.0 · fixed in 2.7.7and 1 other package
  • rubyAlmaLinux:9all versions · fixed in 3.0.7-162.el9_4and 4 other packages
  • rubyAlmaLinux:8all versions · fixed in 3.0.7-143.module_el8.10.0+3852+ce828b19and 4 other packages
  • ruby-bundled-gemsAlmaLinux:9all versions · fixed in 3.1.4-143.module_el9.3.0+60+5ebc989a
  • ruby-bundled-gemsAlmaLinux:8all versions · fixed in 3.1.4-142.module_el8.9.0+3746+91b8233a
  • ruby-irbAlmaLinux:8all versions · fixed in 2.5.9-111.module_el8.9.0+3635+c6f99506
  • rubygem-abrtAlmaLinux:8all versions · fixed in 0.4.0-1.module_el8.10.0+3852+ce828b19and 1 other package

45 more package ranges on OSV.dev

Vendor advisories

  • CVE-2021-33621 Red Hat Product Security904 products fixed · 48 known affected

    ruby/cgi-gem: HTTP response splitting in CGI

    ruby as a component of Red Hat Enterprise Linux 6 · ruby-devel as a component of Red Hat Enterprise Linux 6 · ruby-docs as a component of Red Hat Enterprise Linux 6

  • RHSA-2024:4542 Red Hat Product Security82 products fixed

    Red Hat Security Advisory: ruby security update

  • RHSA-2024:3838 Red Hat Product Security82 products fixed

    Red Hat Security Advisory: ruby security update

  • RHSA-2024:3500 Red Hat Product Security117 products fixed

    Red Hat Security Advisory: ruby:3.0 security update

  • RHSA-2024:1576 Red Hat Product Security133 products fixed

    Red Hat Security Advisory: ruby:3.1 security, bug fix, and enhancement update

  • RHSA-2024:1431 Red Hat Product Security136 products fixed

    Red Hat Security Advisory: ruby:3.1 security, bug fix, and enhancement update

3 more advisories

Full record on NVD

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.

Technical details

Published
2022-11-18

Frequently asked questions

What is CVE-2021-33621?

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.

Is CVE-2021-33621 actively exploited?

Active exploitation of CVE-2021-33621 has not been confirmed. Its EPSS score was 2.4% on 2026-10-19, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-33621?

CVE-2021-33621 has a CVSS v3 base score of 8.8 (HIGH severity).

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