Is CVE-2021-41819 in the CISA KEV catalog?

No. CVE-2021-41819 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2021-41819?

CVE-2021-41819 has a CVSS v3 base score of 7.5 (HIGH).

What is the EPSS score for CVE-2021-41819?

CVE-2021-41819 has an EPSS score of 2.93% (86th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2021-41819?

Upgrade ruby2.7 on debian 11 to 2.7.4-1+deb11u1 or later. Fixes are available for 12 affected products.

CVE & CISA-KEV Catalog

CVE-2021-41819

HIGHEPSS 86th pctl

7.5

CVSS v3

NVD

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.

CWE-565

How to fix

Remediation Available

ruby2.7Debian

Fixed in:2.7.4-1+deb11u1CVE-2021-41819

ruby4Rocky

Fixed in:0-main@noarchRHSA-2026:8838

Fixed in:0-main@x86_64RHSA-2026:8838

Fixed in:0-main@srcRHSA-2026:8838

Fixed in:0-main@aarch64RHSA-2026:8838

ruby4Red Hat / RHEL

Fixed in:0-main@noarchRHSA-2026:8838

Fixed in:0-main@x86_64RHSA-2026:8838

Fixed in:0-main@srcRHSA-2026:8838

Fixed in:0-main@aarch64RHSA-2026:8838

ruby2.3Ubuntu

Fixed in:2.3.1-2~ubuntu16.04.16+esm2USN-5235-1

ruby2.5Ubuntu

Fixed in:2.5.1-1ubuntu1.11USN-5235-1

ruby2.7Ubuntu

Fixed in:2.7.0-5ubuntu1.6USN-5235-1

Ruby 3.0Windows application

Affected:3.0.0 3.0.3Fixed in:3.0.3RubyInstaller Team

Affected:2.7.0 2.7.5Fixed in:2.7.5RubyInstaller Team

Ruby 3.1Windows application

Affected:3.0.0 3.0.3Fixed in:3.0.3RubyInstaller Team

Affected:2.7.0 2.7.5Fixed in:2.7.5RubyInstaller Team

Ruby 3.2Windows application

Affected:2.7.0 2.7.5Fixed in:2.7.5RubyInstaller Team

Affected:3.0.0 3.0.3Fixed in:3.0.3RubyInstaller Team

Ruby 3.2 with MSYS2Windows application

Affected:2.7.0 2.7.5Fixed in:2.7.5RubyInstaller Team

Affected:3.0.0 3.0.3Fixed in:3.0.3RubyInstaller Team

Ruby 3.3Windows application

Affected:2.7.0 2.7.5Fixed in:2.7.5RubyInstaller Team

Affected:3.0.0 3.0.3Fixed in:3.0.3RubyInstaller Team

Ruby 3.3 with MSYS2Windows application

Affected:3.0.0 3.0.3Fixed in:3.0.3RubyInstaller Team

Affected:2.7.0 2.7.5Fixed in:2.7.5RubyInstaller Team

TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityNone

IntegrityHigh

AvailabilityNone

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

Exploit Intelligence

2.93%probability of exploitation in 30 days

86thpercentile

Elevated risk: more likely to be exploited than 86% of all known CVEs.

References

Exploit1

ruby-lang.org

Third-Party Advisory2

Other references3

Related Vulnerabilities

Other CWE-565 vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2026-0257	Critical	9.1	87%	KEV + Ransom	Fix
CVE-2023-35885	Critical	9.8	75%	-	Fix
CVE-2025-64447	High	8.1	7.5%	-	-
CVE-2008-5784	Critical	9.8	7.1%	-	-
CVE-2020-7070	Medium	4.3	5.0%	-	Fix
CVE-2019-7266	Critical	9.8	4.6%	-	-

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2025-05-22.