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CgiApplication · Ruby Lang

CVE-2021-41819

HIGH · 7.5 CVSS v3.1 Published 2022-01-01
Fix available
A fix is available. Upgrade to 2.7.5 / 3.0.3 or later.
See remediation →
84/100
Remediation priority · High
Public exploit Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis

A detailed technical summary for this CVE is being prepared.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
CgiApplication
Affected:= 0.1.0= 0.2.0= 0.3.0
RubyApplication
Affected:<= 2.6.8>= 2.7.0, < 2.7.5>= 3.0.0, < 3.0.3
Software CollectionsApplication
Affected:all versions
Enterprise LinuxOperating system
Affected:= 8.0
Debian LinuxOperating system
Affected:= 9.0= 10.0= 11.0
FedoraOperating system
Affected:= 34= 35
Linux EnterpriseOperating system
Affected:= 11.0= 12.0= 15.0
FactoryApplication
Affected:all versions

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
None

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

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 2.7.5 / 3.0.3 or later
Fixed in 2.7.53.0.3
Recommended fix High confidence

Ruby >= 2.7.5, Ruby >= 3.0.3, or Ruby >= 3.1.0; or CGI gem >= 0.3.1

  1. Identify the current Ruby version by running 'ruby --version'
  2. Identify the current CGI gem version by running 'gem list cgi'
  3. For Ruby: Upgrade to Ruby 2.7.5 or later, or Ruby 3.0.3 or later, or Ruby 3.1.0 or later
  4. For CGI gem: Upgrade to CGI gem version 0.3.1 or later by running 'gem install cgi' and ensuring the Gemfile specifies 'gem "cgi", ">= 0.3.1"'
  5. After upgrade, verify the fix by running 'ruby --version' to confirm the new Ruby version, and 'gem list cgi' to confirm CGI gem version
  6. Restart any running applications or services that use the affected Ruby/CGI gem to ensure the patched version is loaded
Caveat Major Ruby version upgrades (e.g., 2.x to 3.x) may introduce breaking changes in application code; test thoroughly before deploying to production

Generated from the published advisory — verify against the referenced sources before acting.

We can perform the upgrade in your staging environment and verify nothing breaks — typical engagement from $1,950. Get the upgrade done

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-41819 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data