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    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.

    Published:Nov 18, 2022
    Last Modified:Nov 4, 2025
    EPS:Nov 18, 2022
    EPSS Score:0.023
    CVSS Score:8.8

    Affected Products

    Vendor
    Fedoraproject
    Product
    Fedora
    Vendor
    Redhat
    Product
    Enterprise Linux
    Vendor
    Redhat
    Product
    Rhel Eus
    Vendor
    Redhat
    Product
    Rhel Software Collections
    Vendor
    Ruby-lang
    Product
    Cgi
    Vendor
    Ruby-lang
    Product
    Ruby

    Exploits

    https://www.ruby-lang.org/en/news/2022/11/22/http-response-splitting-in-cgi-cve-2021-33621/https://www.ruby-lang.org/en/news/2022/11/22/http-response-splitting-in-cgi-cve-2021-33621/

    Common Attack Pattern Enumeration and Classification (CAPEC)

    CAPEC-10 Buffer Overflow via Environment Variables
    CAPEC-101 Server Side Include (SSI) Injection
    CAPEC-105 HTTP Request Splitting
    CAPEC-108 Command Line Execution through SQL Injection
    CAPEC-120 Double Encoding
    CAPEC-13 Subverting Environment Variable Values
    CAPEC-135 Format String Injection
    CAPEC-14 Client-side Injection-induced Buffer Overflow
    CAPEC-24 Filter Failure through Buffer Overflow
    CAPEC-250 XML Injection
    CAPEC-267 Leverage Alternate Encoding
    CAPEC-273 HTTP Response Smuggling
    CAPEC-28 Fuzzing
    CAPEC-3 Using Leading 'Ghost' Character Sequences to Bypass Input Filters
    CAPEC-31 Accessing/Intercepting/Modifying HTTP Cookies
    CAPEC-34 HTTP Response Splitting
    CAPEC-42 MIME Conversion
    CAPEC-43 Exploiting Multiple Input Interpretation Layers
    CAPEC-45 Buffer Overflow via Symbolic Links
    CAPEC-46 Overflow Variables and Tags
    CAPEC-47 Buffer Overflow via Parameter Expansion
    CAPEC-51 Poison Web Service Registry
    CAPEC-52 Embedding NULL Bytes
    CAPEC-53 Postfix, Null Terminate, and Backslash
    CAPEC-6 Argument Injection
    CAPEC-64 Using Slashes and URL Encoding Combined to Bypass Validation Logic
    CAPEC-67 String Format Overflow in syslog()
    CAPEC-7 Blind SQL Injection
    CAPEC-71 Using Unicode Encoding to Bypass Validation Logic
    CAPEC-72 URL Encoding
    CAPEC-76 Manipulating Web Input to File System Calls
    CAPEC-78 Using Escaped Slashes in Alternate Encoding
    CAPEC-79 Using Slashes in Alternate Encoding
    CAPEC-8 Buffer Overflow in an API Call
    CAPEC-80 Using UTF-8 Encoding to Bypass Validation Logic
    CAPEC-83 XPath Injection
    CAPEC-84 XQuery Injection
    CAPEC-85 AJAX Footprinting
    CAPEC-9 Buffer Overflow in Local Command-Line Utilities

    Related CVEs

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    CVE-2026-35094 (CVSS 3.3) — A flaw was found in libinput. An attacker capable of deploying a Lua plugin file in specific system directorie…
    CVE-2026-35093 (CVSS 8.8) — A flaw was found in libinput. A local attacker who can place a specially crafted Lua bytecode file in certain …
    CVE-2024-3056 (CVSS 7.7) — A flaw was found in Podman. This issue may allow an attacker to create a specially crafted container that, whe…
    CVE-2024-6293 (CVSS 8.8) — Use after free in Dawn in Google Chrome prior to 126.0.6478.126 allowed a remote attacker to potentially explo…
    CVE-2024-6292 (CVSS 8.8) — Use after free in Dawn in Google Chrome prior to 126.0.6478.126 allowed a remote attacker to potentially explo…
    CVE-2024-6291 (CVSS 8.8) — Use after free in Swiftshader in Google Chrome prior to 126.0.6478.126 allowed a remote attacker to potentiall…
    CVE-2024-6290 (CVSS 8.8) — Use after free in Dawn in Google Chrome prior to 126.0.6478.126 allowed a remote attacker to potentially explo…
    CVE-2024-38277 (CVSS 5.4) — A unique key should be generated for a user's QR login key and their auto-login key, so the same key cannot be…

    References

    https://lists.debian.org/debian-lts-announce/2023/06/msg00012.html
    https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/DQR7LWED6VAPD5ATYOBZIGJQPCUBRJBX/
    https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/THVTYHHEOVLQFCFHWURZYO7PVUPBHRZD/
    https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/YACE6ORF2QBXXBK2V2CM36D7TZMEJVAS/
    https://security.gentoo.org/glsa/202401-27
    https://security.netapp.com/advisory/ntap-20221228-0004/
    https://www.ruby-lang.org/en/news/2022/11/22/http-response-splitting-in-cgi-cve-2021-33621/
    https://lists.debian.org/debian-lts-announce/2023/06/msg00012.html
    https://lists.debian.org/debian-lts-announce/2024/09/msg00000.html
    https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/DQR7LWED6VAPD5ATYOBZIGJQPCUBRJBX/
    https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/THVTYHHEOVLQFCFHWURZYO7PVUPBHRZD/
    https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/YACE6ORF2QBXXBK2V2CM36D7TZMEJVAS/
    https://security.gentoo.org/glsa/202401-27
    https://security.netapp.com/advisory/ntap-20221228-0004/
    https://www.ruby-lang.org/en/news/2022/11/22/http-response-splitting-in-cgi-cve-2021-33621/

    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High