CVE-2021-33621

What it is

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.

At a glance

Exploitability

Can be exploited over the network with a low-privilege account. High risk of data exposure, data tampering, service disruption.

Exploit odds

2.5% chance of exploitation in the next 30 days (EPSS).

Fix

No patch or advisory is linked yet. Look at mitigations or restrict exposure.

Timeline

1. 2021-05-28 00:00 UTC ReservedThe CVE id was reserved by its CNA
2. 2022-11-18 23:15 UTC PublishedDisclosed publicly on CVE.org and NVD
3. 2026-06-17 03:54 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 2.5% in the next 30 days (EPSS).
• Severity: 8.8 HIGH (CVSS).
• Fix: none linked yet, which raises it.

Details

Published

2022-11-18 23:15 UTC

Last modified

2026-06-17 03:54 UTC

Exploit probability

2.5% · EPSS, next 30 days

Weakness

CWE-74

Record status

Modified

Affected

• ruby-lang Cgi < 0.1.0.2
• ruby-lang Cgi < 0.2.2
• ruby-lang Cgi < 0.3.5
• Fedoraproject Fedora 35
• Fedoraproject Fedora 36
• Fedoraproject Fedora 37
• ruby-lang Ruby < 2.7.7
• ruby-lang Ruby < 3.0.5

Attack profile CVSS 3.1 · 8.8

Attack vector

Network

Complexity

Low

Privileges needed

Low

User interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2021-33621.md and follow it. Check whether this project is affected by CVE-2021-33621. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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