Skip to content
Noroxi
NVD / CVE Program· CNA mitre

CVE-2021-41819: CGI::Cookie.parse in Ruby through 2.6.8 mishandles security prefixes in cookie names.

Noroxi assessment

Priority: Monitor (action score 31/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 3.1% (FIRST EPSS); higher than 88% of all records.
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: ruby (AlmaLinux:8) 2.5.9-110.module_el8.6.0+3074+4b08f9d4, 2.6.9-108.module_el8.5.0+2623+08a8ba32, 3.0.4-141.module_el8.6.0+3263+41cde0c0; ruby-default-gems (AlmaLinux:8) 3.0.4-141.module_el8.6.0+3263+41cde0c0, 2.7.6-138.module_el8.6.0+3263+904da987; ruby-devel (AlmaLinux:8) 2.7.6-138.module_el8.6.0+3263+904da987, 2.6.9-108.module_el8.5.0+250+ba22dbf7, 2.6.9-108.module_el8.5.0+2623+08a8ba32.
  • Mentioned 2 times in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to ruby (AlmaLinux:8) 2.5.9-110.module_el8.6.0+3074+4b08f9d4, 2.6.9-108.module_el8.5.0+2623+08a8ba32, 3.0.4-141.module_el8.6.0+3263+41cde0c0; ruby-default-gems (AlmaLinux:8) 3.0.4-141.module_el8.6.0+3263+41cde0c0, 2.7.6-138.module_el8.6.0+3263+904da987; ruby-devel (AlmaLinux:8) 2.7.6-138.module_el8.6.0+3263+904da987, 2.6.9-108.module_el8.5.0+250+ba22dbf7, 2.6.9-108.module_el8.5.0+2623+08a8ba32 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

HighCVSS 7.5 · v3.1—No exploit Fix available
Published
Jan 1, 2022
Updated
Jun 17, 2026
EPSS
3.1% · 88th percentile

Report tools

JSON

Action score

31

Monitor

Low priority for now.

CVSS
30 / 40 · 7.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
1 / 30 · 3.1%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2021-41819

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

One daily email digest (06:00 UTC); connect a webhook for KEV listings and weaponized exploits instantly.

Your free account also gets you

Running WordPress? Scan your site free with WP Lens

  • Stack alerts: add the products and versions you run, get the new CVEs that affect them
  • Uptime monitoring: 1 site, instant email when it goes down
  • Add your domain: subdomains and takeover risk scanned every week (1 domain)
  • 10 scans an hour on the security tools (3 a day without an account), an API key and MCP
  • All your scans in one panel: findings, what changed in the last scan, a report per domain or per client (PDF, share link)
All free tools

Sign up with email · Have an account? Sign in

Free account, no card. Unfollow any time.

Don't want an account? Get "Exploited this week" by email every MondayDon't want an account? RSS feed for ruby-lang records

Running WordPress? Scan your site free with WP Lens

Is your version affected? Check it

Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

We use this product, ask for help

Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
ruby-langcgi
ruby-langruby
redhatsoftware collections
redhatenterprise linux
debiandebian linux
suselinux enterprise
opensusefactory
opensuseleap
fedoraprojectfedora

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • debian debian linux10.0
  • debian debian linux11.0
  • debian debian linux9.0
  • fedoraproject fedora34
  • fedoraproject fedora35
  • opensuse factoryall versions
  • opensuse leap15.2
  • redhat enterprise linux8.0
  • redhat software collectionsall versions
  • ruby-lang cgi0.1.0
  • ruby-lang cgi0.2.0
  • ruby-lang cgi0.3.0
  • ruby-lang ruby3.0.0 and later · before 3.0.3
  • ruby-lang ruby2.7.0 and later · before 2.7.5
  • ruby-lang rubyup to 2.6.8 inclusive
  • suse linux enterprise11.0
  • suse linux enterprise12.0
  • suse linux enterprise15.0

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
AlmaLinux:8rubybefore 2.5.9-110.module_el8.6.0+3074+4b08f9d42.5.9-110.module_el8.6.0+3074+4b08f9d4
AlmaLinux:8rubybefore 2.6.9-108.module_el8.5.0+2623+08a8ba322.6.9-108.module_el8.5.0+2623+08a8ba32
AlmaLinux:8rubybefore 3.0.4-141.module_el8.6.0+3263+41cde0c03.0.4-141.module_el8.6.0+3263+41cde0c0
AlmaLinux:8rubybefore 2.6.9-108.module_el8.5.0+250+ba22dbf72.6.9-108.module_el8.5.0+250+ba22dbf7
AlmaLinux:8rubybefore 2.7.6-138.module_el8.6.0+3263+904da9872.7.6-138.module_el8.6.0+3263+904da987
AlmaLinux:8ruby-default-gemsbefore 3.0.4-141.module_el8.6.0+3263+41cde0c03.0.4-141.module_el8.6.0+3263+41cde0c0
AlmaLinux:8ruby-default-gemsbefore 2.7.6-138.module_el8.6.0+3263+904da9872.7.6-138.module_el8.6.0+3263+904da987
AlmaLinux:8ruby-develbefore 2.7.6-138.module_el8.6.0+3263+904da9872.7.6-138.module_el8.6.0+3263+904da987
AlmaLinux:8ruby-develbefore 2.6.9-108.module_el8.5.0+250+ba22dbf72.6.9-108.module_el8.5.0+250+ba22dbf7
AlmaLinux:8ruby-develbefore 2.6.9-108.module_el8.5.0+2623+08a8ba322.6.9-108.module_el8.5.0+2623+08a8ba32
AlmaLinux:8ruby-develbefore 3.0.4-141.module_el8.6.0+3263+41cde0c03.0.4-141.module_el8.6.0+3263+41cde0c0
AlmaLinux:8ruby-develbefore 2.5.9-110.module_el8.6.0+3074+4b08f9d42.5.9-110.module_el8.6.0+3074+4b08f9d4
AlmaLinux:8ruby-docbefore 2.7.6-138.module_el8.6.0+3263+904da9872.7.6-138.module_el8.6.0+3263+904da987
AlmaLinux:8ruby-docbefore 2.6.9-108.module_el8.5.0+250+ba22dbf72.6.9-108.module_el8.5.0+250+ba22dbf7
AlmaLinux:8ruby-docbefore 2.6.9-108.module_el8.5.0+2623+08a8ba322.6.9-108.module_el8.5.0+2623+08a8ba32
AlmaLinux:8ruby-docbefore 3.0.4-141.module_el8.6.0+3263+41cde0c03.0.4-141.module_el8.6.0+3263+41cde0c0
AlmaLinux:8ruby-docbefore 2.5.9-110.module_el8.6.0+3074+4b08f9d42.5.9-110.module_el8.6.0+3074+4b08f9d4
AlmaLinux:8ruby-irbbefore 2.5.9-110.module_el8.6.0+3074+4b08f9d42.5.9-110.module_el8.6.0+3074+4b08f9d4
AlmaLinux:8ruby-libsbefore 2.7.6-138.module_el8.6.0+3263+904da9872.7.6-138.module_el8.6.0+3263+904da987
AlmaLinux:8ruby-libsbefore 2.5.9-110.module_el8.6.0+3074+4b08f9d42.5.9-110.module_el8.6.0+3074+4b08f9d4
AlmaLinux:8ruby-libsbefore 2.6.9-108.module_el8.5.0+250+ba22dbf72.6.9-108.module_el8.5.0+250+ba22dbf7
AlmaLinux:8ruby-libsbefore 3.0.4-141.module_el8.6.0+3263+41cde0c03.0.4-141.module_el8.6.0+3263+41cde0c0
AlmaLinux:8ruby-libsbefore 2.6.9-108.module_el8.5.0+2623+08a8ba322.6.9-108.module_el8.5.0+2623+08a8ba32
AlmaLinux:8rubygem-abrtbefore 0.3.0-4.module_el8.5.0+2625+ec4185530.3.0-4.module_el8.5.0+2625+ec418553

+96

Same product

ruby-lang: all records

Other highest-scoring records for the same primary product.

  • CVE-2021-41816CGI.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 long string on platfor
    40Plan
  • CVE-2021-33621The 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.
    36Monitor
  • CVE-2025-27220In the CGI gem before 0.4.2 for Ruby, a Regular Expression Denial of Service (ReDoS) vulnerability exists in the Util#escapeElement method.
    30Monitor

Published before and after this one in the same product

  • Later →CVE-2025-27219Mar 3, 2025 · In the CGI gem before 0.4.2 for Ruby, the CGI::Cookie.parse method in the CGI library contains a potential Denial of Service (DoS) vulnerabi
    30Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
almalinux:ruby2.6.9-108.module_el8.5.0+250+ba22dbf7 · AlmaLinux:8Package registry (OSV)
almalinux:ruby-devel2.6.9-108.module_el8.5.0+2623+08a8ba32 · AlmaLinux:8Package registry (OSV)
almalinux:ruby-doc2.6.9-108.module_el8.5.0+250+ba22dbf7 · AlmaLinux:8Package registry (OSV)
almalinux:ruby-libs2.6.9-108.module_el8.5.0+2623+08a8ba32 · AlmaLinux:8Package registry (OSV)
almalinux:rubygem-abrt0.3.0-4.module_el8.5.0+259+8cec6917 · AlmaLinux:8Package registry (OSV)
almalinux:rubygem-abrt-doc0.3.0-4.module_el8.5.0+259+8cec6917 · AlmaLinux:8Package registry (OSV)
almalinux:rubygem-bigdecimal1.4.1-108.module_el8.5.0+2623+08a8ba32 · AlmaLinux:8Package registry (OSV)
almalinux:rubygem-bson4.5.0-1.module_el8.5.0+2623+08a8ba32 · AlmaLinux:8Package registry (OSV)
almalinux:rubygem-bson-doc4.5.0-1.module_el8.5.0+250+ba22dbf7 · AlmaLinux:8Package registry (OSV)
almalinux:rubygem-bundler1.17.2-108.module_el8.5.0+2623+08a8ba32 · AlmaLinux:8Package registry (OSV)
almalinux:rubygem-did_you_mean1.3.0-108.module_el8.5.0+2623+08a8ba32 · AlmaLinux:8Package registry (OSV)
almalinux:rubygem-io-console0.4.7-108.module_el8.5.0+2623+08a8ba32 · AlmaLinux:8Package registry (OSV)
alpine:ruby2.7.5-r0 · Alpine:v3.12Package registry (OSV)
debian:ruby2.32.3.3-1+deb9u11 · Debian:9Package registry (OSV)
debian:ruby2.52.5.5-3+deb10u4 · Debian:10Package registry (OSV)
debian:ruby2.72.7.4-1+deb11u1 · Debian:11Package registry (OSV)
opensuse:ruby2.52.5.9-150000.4.26.1 · openSUSE:Leap 15.3Package registry (OSV)
opensuse:ruby2.72.7.5-1.1 · openSUSE:TumbleweedPackage registry (OSV)
opensuse:ruby3.03.0.3-1.1 · openSUSE:TumbleweedPackage registry (OSV)
opensuse:ruby3.13.1.0-1.1 · openSUSE:TumbleweedPackage registry (OSV)
opensuse:ruby3.23.2.1-1.1 · openSUSE:TumbleweedPackage registry (OSV)
opensuse:ruby3.33.3.0-1.2 · openSUSE:TumbleweedPackage registry (OSV)
opensuse:ruby3.43.4.1-1.1 · openSUSE:TumbleweedPackage registry (OSV)
opensuse:ruby4.04.0.0~preview2-1.1 · openSUSE:TumbleweedPackage registry (OSV)
red hat:ruby0:2.6.9-108.module+el8.5.0+13719+08a8ba32 · Red Hat:enterprise_linux:8::appstreamPackage registry (OSV)
red hat:ruby-debuginfo0:2.6.9-108.module+el8.5.0+13719+08a8ba32 · Red Hat:enterprise_linux:8::appstreamPackage registry (OSV)
red hat:ruby-debugsource0:2.6.9-108.module+el8.5.0+13719+08a8ba32 · Red Hat:enterprise_linux:8::appstreamPackage registry (OSV)
red hat:ruby-devel0:2.6.9-108.module+el8.5.0+13719+08a8ba32 · Red Hat:enterprise_linux:8::appstreamPackage registry (OSV)
red hat:ruby-doc0:2.6.9-108.module+el8.5.0+13719+08a8ba32 · Red Hat:enterprise_linux:8::appstreamPackage registry (OSV)
red hat:ruby-libs0:2.6.9-108.module+el8.5.0+13719+08a8ba32 · Red Hat:enterprise_linux:8::appstreamPackage registry (OSV)

+17

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

The product’s vendor appears in a public program. Matched by name; verify the scope text in the program.

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

All national notices →

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
high · data or configuration can be modified
Availability
none
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
High
Availability impact
None

Weakness class (CWE)

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

CVSS vector

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

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (4 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records