How severe is CVE-2021-41819?

CVE-2021-41819 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity high, and availability none.

Is CVE-2021-41819 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (85th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-41819?

CVE-2021-41819 primarily affects Ruby-lang Cgi. In total, 16 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-41819?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2021-41819 published?

CVE-2021-41819 was published on 2022-01-01 and last updated on 2026-06-17.

CVE-2021-41819

CVE-2021-41819 is a high-severity vulnerability in Ruby-lang Cgi with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-565.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v2: 5.0
EPSS exploit prediction: 3% (85th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-565
Affected product: Ruby-lang Cgi
Published: 2022-01-01
Last modified: 2026-06-17

Description

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.

Frequently asked questions

What is CVE-2021-41819?: 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.
How severe is CVE-2021-41819?: CVE-2021-41819 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity high, and availability none.
Is CVE-2021-41819 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (85th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-41819?: CVE-2021-41819 primarily affects Ruby-lang Cgi. In total, 16 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-41819?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-41819 published?: CVE-2021-41819 was published on 2022-01-01 and last updated on 2026-06-17.

References

Affected products (16)

cpe:2.3:a:ruby-lang:cgi:0.1.0:*:*:*:*:ruby:*:*
cpe:2.3:a:ruby-lang:cgi:0.2.0:*:*:*:*:ruby:*:*
cpe:2.3:a:ruby-lang:cgi:0.3.0:*:*:*:*:ruby:*:*
cpe:2.3:a:ruby-lang:ruby:*:*:*:*:*:*:*:*
cpe:2.3:a:redhat:software_collections:-:*:*:*:*:*:*:*
cpe:2.3:o:redhat:enterprise_linux:8.0:*:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:11.0:*:*:*:*:*:*:*
cpe:2.3:o:suse:linux_enterprise:11.0:sp1:*:*:*:*:*:*
cpe:2.3:o:suse:linux_enterprise:12.0:*:*:*:*:*:*:*
cpe:2.3:o:suse:linux_enterprise:15.0:*:*:*:*:*:*:*
cpe:2.3:a:opensuse:factory:-:*:*:*:*:*:*:*
cpe:2.3:o:opensuse:leap:15.2:*:*:*:*:*:*:*
cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*
cpe:2.3:o:fedoraproject:fedora:35:*:*:*:*:*:*:*

More vulnerabilities in Ruby-lang Cgi

CVE-2021-41816 — Critical (CVSS 9.8): CGI.escape_html in Ruby before 2.7.5 and 3.x before 3.0.3 has an integer overflow and resultant buffer overflow via a…
CVE-2021-33621 — High (CVSS 8.8): 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…
CVE-2025-27219 — Medium (CVSS 5.8): In the CGI gem before 0.4.2 for Ruby, the CGI::Cookie.parse method in the CGI library contains a potential Denial of…
CVE-2025-27220 — Medium (CVSS 4.0): In the CGI gem before 0.4.2 for Ruby, a Regular Expression Denial of Service (ReDoS) vulnerability exists in the…

All CVEs affecting Ruby-lang Cgi →

Other CWE-565 vulnerabilities

CVE-2023-41084 — Critical (CVSS 10.0): Session management within the web application is incorrect and allows attackers to steal session cookies to perform a…
CVE-2014-125112 — Critical (CVSS 9.8): Plack::Middleware::Session::Cookie versions through 0.21 for Perl allows remote code…
CVE-2022-50926 — Critical (CVSS 9.8): WAGO 750-8212 PFC200 G2 2ETH RS firmware contains a privilege escalation vulnerability that allows attackers to…
CVE-2025-65212 — Critical (CVSS 9.8): An issue was discovered in NJHYST HY511 POE core before 2.1 and plugins before 0.1. The vulnerability stems from the…
CVE-2025-14440 — Critical (CVSS 9.8): The JAY Login & Register plugin for WordPress is vulnerable to authentication bypass in versions up to, and including,…
CVE-2025-2395 — Critical (CVSS 9.8): The U-Office Force from e-Excellence has an Improper Authentication vulnerability, allowing unauthenticated remote…

Browse all CWE-565 vulnerabilities →