RackApplication
CVE-2026-34763
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 · uneditedRack is a modular Ruby web server interface. Prior to versions 2.2.23, 3.1.21, and 3.2.6, Rack::Directory interpolates the configured root path directly into a regular expression when deriving the displayed directory path. If root contains regex metacharacters such as +, *, or ., the prefix stripping can fail and the generated directory listing may expose the full filesystem path in the HTML output. 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 confidenceRack::Directory interpolates the configured root path directly into a regular expression without escaping regex metacharacters (+, *, .). When the root contains such characters, the prefix stripping fails and the generated HTML directory listing exposes the full filesystem path instead of the relative path.
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
< 2.2.23>= 3.0.0, < 3.1.21>= 3.2.0, < 3.2.6CVSS 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
- Low
- Integrity
- None
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/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 checksWork through these to decide whether this CVE applies to you.
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Check installed Rack versionRun `ruby -e "puts Rack::VERSION"` or check the Gemfile.lock for the rack gem version, or run `gem list rack`Affected if Version is < 2.2.23 OR (>= 3.0.0 AND < 3.1.21) OR (>= 3.2.0 AND < 3.2.6)
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Confirm Rack::Directory middleware is in useSearch application code and configuration files for `Rack::Directory`, `use Rack::Directory`, or `Rack::Static` with directory listing enabledAffected if Rack::Directory middleware or static file serving with directory listing is configured and active
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Identify the configured root path for directory servingLocate the root path argument passed to Rack::Directory (e.g., `Rack::Directory.new('/path/to/root')`) in your application code or configurationAffected if A root path is configured for the directory middleware
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Inspect root path for regex metacharactersExamine the configured root path string for unescaped characters: + (plus), * (asterisk), or . (dot). For example, a path like /var/www+site or /path/to*files contains these characters.Affected if The root path contains any unescaped regex metacharacters (+, *, or .)
User is affected if running a vulnerable Rack version AND using Rack::Directory with a root path that contains unescaped regex metacharacters (+, *, or .), causing full filesystem paths to be exposed in HTML directory listings.
Generated from the published advisory. Verify against your own configuration.
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 · scoped2.2.233.1.213.2.6
Upgrade Rack to versions 2.2.23, 3.1.21, or 3.2.6 which properly escape regex metacharacters in the root path before interpolation.
Rack 3.2.6 (or 2.2.23/3.1.21 depending on current major version)
- Identify the current Rack gem version in your Gemfile or Gemfile.lock
- Determine the appropriate upgrade path based on your current major version: if using Rack 2.x, upgrade to 2.2.23; if using Rack 3.0.x or 3.1.x, upgrade to 3.1.21; if using Rack 3.2.x, upgrade to 3.2.6
- Run `bundle update rack` or manually update the version in your Gemfile to the chosen fixed version
- Run `bundle install` to update dependencies
- Verify the application starts and middleware functions correctly
- Test the Rack::Directory middleware if used to confirm paths are properly sanitized in the HTML output
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Rack
Scoped from the published advisory
- Consultation3.0 h
- Implementation2.0 h
- Testing6.0 h
- Review / QA3.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,840.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-34763 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-34763 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- 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
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