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CVE-2021-41819

26
FAUCET Score

CVE-2021-41819 describes a vulnerability in CGI::Cookie.parse in Ruby (through 2.6.8) and the CGI gem (through 0.3.0), where security prefixes in cookie names are mishandled, affecting various Linux distributions and Ruby itself. This high-severity vulnerability (CVSS 7.5) can be exploited remotely with low complexity and no user interaction, leading to high integrity impacts. Despite its severity, there is no evidence of active exploitation, no public exploit code (Metasploit, Nuclei, ExploitDB), and minimal community discussion or media coverage.

Impacted Technologies

VendorProductVersion(s)CPE
0.1.0CPE matchmatch criteria
cpe:2.3:a:ruby-lang:cgi:0.1.0:*:*:*:*:ruby:*:*
0.2.0CPE matchmatch criteria
cpe:2.3:a:ruby-lang:cgi:0.2.0:*:*:*:*:ruby:*:*
0.3.0CPE matchmatch criteria
cpe:2.3:a:ruby-lang:cgi:0.3.0:*:*:*:*:ruby:*:*
<= 2.6.8CPE matchmatch criteria
cpe:2.3:a:ruby-lang:ruby:*:*:*:*:*:*:*:*
>= 2.7.0, < 2.7.5CPE matchmatch criteria
cpe:2.3:a:ruby-lang:ruby:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

7.5HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
HIGH
Availability Impact
NONE
Exploitability Score
3.9
Impact Score
3.6
CvssVersion
3.1

Exploit Intelligence

EPSS Score
2.93%
Probability of exploitation in next 30 days
EPSS Percentile
85.6%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0293 is in the 74th percentile among its peer group of 51,551 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.1 Mastodon, and 0.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (15)

microsoftpatch availablevia msrc
Product: 19482-16823Fixed in: 3.1.2-2
microsoftpatch availablevia msrc
Product: cbl2 ruby 3.1.2-2 on CBL Mariner 2.0Fixed in: 3.1.2-2
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8Fixed in: ruby:3.0-8060020220810162001.ad008a3a
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Software Collections for Red Hat Enterprise Linux 7Fixed in: rh-ruby26-ruby-0:2.6.9-120.el7
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Software Collections for Red Hat Enterprise Linux 7Fixed in: rh-ruby30-ruby-0:3.0.4-149.el7
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Software Collections for Red Hat Enterprise Linux 7Fixed in: rh-ruby27-ruby-0:2.7.6-131.el7
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8Fixed in: ruby:2.6-8050020211215144356.c5368500
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8Fixed in: ruby:2.5-8060020220715152618.ad008a3a
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8Fixed in: ruby:2.7-8060020220728151401.ad008a3a
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8.1 Update Services for SAP SolutionsFixed in: ruby:2.6-8010020220201152941.c27ad7f8
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8.2 Extended Update SupportFixed in: ruby:2.6-8020020220201131207.4cda2c84
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8.4 Extended Update SupportFixed in: ruby:2.6-8040020220131135901.522a0ee4
View patch
rubygemspatch availablevia ghsa
Product: cgiFixed in: 0.1.0.1
rubygemspatch availablevia ghsa
Product: cgiFixed in: 0.2.1
rubygemspatch availablevia ghsa
Product: cgiFixed in: 0.3.1

Vendor Advisories (3)

rubygemsGHSA-4vf4-qmvg-mh7hhigh

Cookie Prefix Spoofing in CGI::Cookie.parse

Jan 21, 2022
microsoft2022-Jan/CVE-2021-41819Important

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.

Jan 11, 2022
redhatCVE-2021-41819Moderate

ruby: Cookie prefix spoofing in CGI::Cookie.parse

Nov 24, 2021

References

hackerone.com / reports/910552
Permissions RequiredThird Party Advisory
lists.fedoraproject.org / archives/list/package-announce%40lists.fedoraproject.org/message/IUXQCH6FRKANCVZO2Q7D2SQX33FP3KWN
lists.fedoraproject.org / archives/list/package-announce%40lists.fedoraproject.org/message/UTOJGS5IEFDK3UOO7IY4OTTFGHGLSWZF
security.gentoo.org / glsa/202401-27
security.netapp.com / advisory/ntap-20220121-0003
Third Party Advisory
ruby-lang.org / en/news/2021/11/24/cookie-prefix-spoofing-in-cgi-cookie-parse-cve-2021-41819
ExploitVendor Advisory