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RackApplication

CVE-2026-34785

HIGH · 7.5 CVSS v3.1 Published 2026-04-02
Fix available
A fix is available. Upgrade to 2.2.23 / 3.1.21 or later.
See remediation →
84/100
Remediation priority · High
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
Rack is a modular Ruby web server interface. Prior to versions 2.2.23, 3.1.21, and 3.2.6, Rack::Static determines whether a request should be served as a static file using a simple string prefix check. When configured with URL prefixes such as "/css", it matches any request path that begins with that string, including unrelated paths such as "/css-config.env" or "/css-backup.sql". As a result, files under the static root whose names merely share the configured prefix may be served unintentionally, leading to information disclosure. This issue has been patched in versions 2.2.23, 3.1.21, and 3.2.6.

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 · high confidence

Rack::Static uses a simple string prefix check to determine if a request should be served as a static file. When configured with prefixes like '/css', it incorrectly matches any path beginning with that string, including unrelated files like '/css-config.env' or '/css-backup.sql', leading to unintended disclosure of files under the static root.

MitigationUpgrade Rack to versions 2.2.23, 3.1.21, or 3.2.6 or later. Review static file configurations to ensure only intended directories are exposed and consider using more specific path matching.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

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
RackApplication
Affected:< 2.2.23>= 3.0.0, < 3.1.21>= 3.2.0, < 3.2.6

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
High
Integrity
None
Availability
None

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check installed Rack gem version
    Run 'gem list rack' or in Ruby code: puts Gem.loaded_specs['rack'].version.to_s
    Affected if Version is < 2.2.23, or >= 3.0.0 and < 3.1.21, or >= 3.2.0 and < 3.2.6
  2. Identify if Rack::Static middleware is in use
    Search application code for 'Rack::Static' or inspect middleware stack via Rails console: Rails.application.config.middleware.select { |m| m.name.include?('Static') }
    Affected if Rack::Static is loaded in the middleware stack
  3. Review static file prefix configuration
    Search config files and code for Rack::Static options, looking for :root and :prefixes parameters, for example: use Rack::Static, urls: ['/css', '/js'], root: 'public'
    Affected if Prefixes are configured that could match files beyond the intended directory (e.g., '/css' matches '/css-config.env')
  4. Identify sensitive files matching configured prefixes
    List files in the static root directory that begin with any configured prefix strings, for example: ls public/ | grep '^css' if '/css' prefix is configured
    Affected if Sensitive files (such as .env, .sql, .backup, configuration files) exist whose names start with a static file prefix

The environment is affected if a vulnerable Rack version is running AND Rack::Static is configured with prefixes that would unintentionally match sensitive files outside the intended static directories.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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 2.2.23 / 3.1.21 / 3.2.6 or later
Fixed in 2.2.233.1.213.2.6
Interim mitigation

Upgrade Rack to versions 2.2.23, 3.1.21, or 3.2.6 or later. Review static file configurations to ensure only intended directories are exposed and consider using more specific path matching.

Recommended fix High confidence

Rack 2.2.23, 3.1.21, or 3.2.6 (select based on your current major version)

  1. Check the current Rack version in your Gemfile or gem list
  2. Update the Rack gem to version 2.2.23 (for Rack 2.x), 3.1.21 (for Rack 3.0.x-3.1.x), or 3.2.6 (for Rack 3.2.x)
  3. Run bundle update rack or gem install rack with the appropriate version
  4. Restart the application to load the new gem version
  5. Verify the fix by testing that static file serving now requires proper path matching (e.g., /css/ should not match /css-config.env)

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

Fix this in Rack Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing2.0 h
  • Review / QA1.0 h
7.0 hours of engineering $1,240
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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-2026-34785 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