CVE-2021-41819

Exp

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.

Published: 2022-01-01 Last update: 2025-05-22 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-41819 is rated High Exploit Risk (70.6/100): CVSS High severity, with medium exploitation likelihood (EPSS 0.76%). 1 public exploit reference(s) are indexed (Exploit-DB). Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2021-41819

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2021-41819

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-03-11 0.68% 0.76% +0.07%
2 2026-03-04 0.45% 0.68% +0.23%
3 2026-03-01 — 0.45% —

Full EPSS history (44 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-41819

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:N)
Service keeps running; no real outage angle.
 3.9 3.6 [email protected]
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:N)
Service keeps running; no real outage angle.
 3.9 3.6 134c704f-9b21-4f2e-91b3-4a467353bcc0
5.0 2.0 MEDIUM
AV:N/AC:L/Au:N/C:N/I:P/A:N Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:N)
No availability impact.
 10.0 2.9 [email protected]

Weakness enumeration for CVE-2021-41819

GitHub Security Advisory for CVE-2021-41819

GHSA-4vf4-qmvg-mh7h · Severity: high · Ecosystem: rubygems — Cookie Prefix Spoofing in CGI::Cookie.parse

OS Trackers for CVE-2021-41819

vendor priority summary link
alpine — CVE-2021-41819: 1 source package rows (ruby); 55 state rows across 8 repos (3.12-main, 3.17-main, 3.18-main, 3.19-main, 3.20-main, 3.21-main, 3.22-main, edge-main); fixed 8, open 47. https://security.alpinelinux.org/vuln/CVE-2021-41819
debian not yet assigned CVE-2021-41819 not yet assigned priority: Debian including 1 source packages (ruby2.7), 1 status rows across 1 suites (bullseye): resolved 1. https://security-tracker.debian.org/tracker/CVE-2021-41819
gentoo normal CVE-2021-41819: 1 GLSA(s) (202401-27), 1 atom(s) (dev-lang/ruby); latest impact normal. https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2021-41819
redhat medium — https://access.redhat.com/security/cve/CVE-2021-41819
suse medium CVE-2021-41819 severity moderate: SUSE including 348 source package names (2.17-17.3:libruby2_5-2_5-2.5.9-150000.4.26.1, 2.17-17.3:ruby2.5-2.5.9-150000.4.26.1, …), 920 product×package rows across 201 product lines (Container bci/ruby, Container suse/rmt-server, … (201 product lines)): Fixed 683, Known Affected 205, Will Not Fix 32. https://www.suse.com/security/cve/CVE-2021-41819/
ubuntu medium CVE-2021-41819 medium priority: Ubuntu including 4 source packages (ruby2.3, ruby2.5, ruby2.7, ruby3.0), 17 status rows across 8 suites (bionic, focal, hirsute, impish, jammy, trusty, upstream, xenial): ignored 7, released 6, needs-triage 4. https://ubuntu.com/security/CVE-2021-41819

Affected software / configurations for CVE-2021-41819

Vendor Product Version Raw CPE
ruby-lang cgi 0.1.0 cpe:2.3:a:ruby-lang:cgi:0.1.0:*:*:*:*:ruby:*:*
ruby-lang cgi 0.2.0 cpe:2.3:a:ruby-lang:cgi:0.2.0:*:*:*:*:ruby:*:*
ruby-lang cgi 0.3.0 cpe:2.3:a:ruby-lang:cgi:0.3.0:*:*:*:*:ruby:*:*
ruby-lang ruby <= 2.6.8 cpe:2.3:a:ruby-lang:ruby:*:*:*:*:*:*:*:*
ruby-lang ruby >= 2.7.0, < 2.7.5 cpe:2.3:a:ruby-lang:ruby:*:*:*:*:*:*:*:*
ruby-lang ruby >= 3.0.0, < 3.0.3 cpe:2.3:a:ruby-lang:ruby:*:*:*:*:*:*:*:*
redhat software_collections — cpe:2.3:a:redhat:software_collections:-:*:*:*:*:*:*:*
redhat enterprise_linux 8.0 cpe:2.3:o:redhat:enterprise_linux:8.0:*:*:*:*:*:*:*
debian debian_linux 9.0 cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*
debian debian_linux 10.0 cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*
debian debian_linux 11.0 cpe:2.3:o:debian:debian_linux:11.0:*:*:*:*:*:*:*
suse linux_enterprise 11.0 cpe:2.3:o:suse:linux_enterprise:11.0:sp1:*:*:*:*:*:*
suse linux_enterprise 12.0 cpe:2.3:o:suse:linux_enterprise:12.0:*:*:*:*:*:*:*
suse linux_enterprise 15.0 cpe:2.3:o:suse:linux_enterprise:15.0:*:*:*:*:*:*:*
opensuse factory — cpe:2.3:a:opensuse:factory:-:*:*:*:*:*:*:*
opensuse leap 15.2 cpe:2.3:o:opensuse:leap:15.2:*:*:*:*:*:*:*
fedoraproject fedora 34 cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*
fedoraproject fedora 35 cpe:2.3:o:fedoraproject:fedora:35:*:*:*:*:*:*:*

References for CVE-2021-41819

cvelogic Threat Intelligence