Home/CVE/CGI::Cookie.parse in Ruby through 2.6.8 mishandles security prefixes in cookie names. This also affects the CGI gem thro
CVE

CVE-2021-41819

CGI::Cookie.parse in Ruby through 2.6.8 mishandles security prefixes in cookie names. This also affects the CGI gem thro

CGI::Cookie.parse in Ruby through 2.6.8 mishandles security prefixes in cookie names. This also affects the CGI gem through 0.3.0 for Ruby.

HIGH · CVSS 7.5 EPSS 0.00765
Act now
  • Public exploit or PoC is available
  • CVSS base score ≥ 7.0
Sigma rules3 YARA rules0
⬡

Weakness Classification

CWE-565Reliance on Cookies without Validation and Integrity Checking
CWE-565Reliance on Cookies without Validation and Integrity Checking
▤

Affected Products & Versions

11
ruby-lang cgiall versions
ruby-lang ruby<= 2.6.8
ruby-lang ruby>= 2.7.0 and < 2.7.5
ruby-lang ruby>= 3.0.0 and < 3.0.3
redhat software collectionsall versions
redhat enterprise linuxall versions
debian linuxall versions
suse linux enterpriseall versions
▤

Affected Packages

1
Language-ecosystem packages (from OSV) tied to this CVE, with the version that fixes it - the dependency-level detail NVD doesn’t carry.
RubyGems cgi HIGH fixed in 0.3.1
⚠

Public Exploits & PoCs

1
pocwww.ruby-lang.org · cookie-prefix-spoofing-in-cgi-cookie-parse-cve-2021-41819www.ruby-lang.org
◈

Sigma Hunt Rules

3
Exact rules name this CVE ID. Product rules name an affected product in their title. Related rules cover techniques used by actors who exploited this CVE. Showing the most relevant matches; the complete related set is on the full drill-down.
productmediumRuby on Rails Framework Exceptions
productmediumPotential Ruby Reverse Shell
productmediumRuby Inline Command Execution
▣

Scoring & Timeline

7.5
HIGH · CVSS v3.1 · cve@mitre.org
View on NVD
Attack Vector
Network Adjacent Local Physical
Attack Complexity
Low High
Privileges Required
None Low High
User Interaction
None Required
Scope
Unchanged Changed
Confidentiality
None Low High
Integrity
None Low High
Availability
None Low High
Published to NVD01 Jan 2022 · 06:15 AM
CVSS VectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
SSVC triage · cisa-vulnrichment
Exploitation
none
Automatable
no
Technical impact
partial
SSVC asks the questions that actually drive patch urgency: is it being exploited, can attacks be automated, and how total is the impact.
⚑

Vendor Advisories

23
rhsaRHSA-2026:7307Moderate
rhsaRHSA-2026:8838Moderate
rhsaRHSA-2026:7305Moderate
suse-csafopenSUSE-SU-2025:15819-1
suse-csafopenSUSE-SU-2025:14621-1
🔗

References & Sources

5
Source URLs (vendor pages, mailing lists, write-ups). Exploit/PoC links are in their own section above to avoid duplication.
https://hackerone.com/reports/910552Permissions RequiredThird Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/IUXQCH6FRKANCVZO2Q7D2SQX33FP3KWN/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/UTOJGS5IEFDK3UOO7IY4OTTFGHGLSWZF/
https://security.gentoo.org/glsa/202401-27
https://security.netapp.com/advisory/ntap-20220121-0003/Third Party Advisory
Intelligence Graph · click any node to traverse
CVETechnique ActorTool Family
drag to reposition · click any node to traverse · button top-right enlarges
External lookups - second-class, for what we don’t hold ourselves
NVDCVE.orgCISAVulnersExploit-DBGitHub PoCVulnCheck KEVGreyNoise
Vulnerabilities
CISA KEV catalog
CWE weaknesses
CAPEC attack patterns
Package vulnerabilities
Threat intelligence
Threat actors
Tools & malware
ATT&CK techniques
IOCs
Detection & defense
Sigma rules
YARA rules
Atomic Red Team tests
D3FEND countermeasures
Compliance
NIST 800-53
ISO 27001:2022
SOC 2 TSC
PCI-DSS v4.0
CIS Controls v8.1
About
All capabilities
Live statistics
Data sources
Privacy policy
Terms of service
threatengine.sh  ·  Open-source threat intelligence platform  ·  100+ authoritative sources  ·  Every fact traces to its origin