Rack has a root directory disclosure via unescaped regex interpolation in Rack::Directory

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

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

EPSS

• CVE-2026-34763: 0.25% estimated exploitation activity in the next 30 days; percentile 16.41 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary 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. Details Rack::Directory::DirectoryBody#each computes the visible path using code equivalent to: Here, root is a developer-configured filesystem path. It is normalized earlier with File.expandpath(root) and then inserted directly into a regular expression without escaping. Because the value is treated as regex syntax rather than as a literal string, metacharacters in the configured path can change how the prefix match behaves. When that happens, the expected root prefix is not removed from path, and the absolute filesystem path is rendered into the HTML directory listing. Impact If Rack::Directory is configured to serve a directory whose absolute path contains regex…

Published by the source

2 Apr 2026, 20:32 UTC

Last modified by the source

13 May 2026, 16:18 UTC

Source last checked

26 Oct 2026, 15:52 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-7mqq-6cf9-v2qp

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# Patch Next advisory brief: CVE-2026-34763

Advisory: Rack has a root directory disclosure via unescaped regex interpolation in Rack::Directory
IDs: CVE-2026-34763, GHSA-7mqq-6cf9-v2qp
Record: https://patchnext.com/advisories/cve-2026-34763 (revision 1, source checked 26 Oct 2026, 15:52 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: rack 3.2.6, 3.1.21, 2.2.23. A vendor fix does not mean a deployment is fixed.

## Affected components
- RubyGems rack: affected < 2.2.23; >= 3.0.0.beta1, < 3.1.21; >= 3.2.0, < 3.2.6; fixed in 3.1.21, 2.2.23, 3.2.6

## Suggested inspection (read-only)
- RubyGems rack: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on rack.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-7mqq-6cf9-v2qp (GitHub-reviewed advisory GHSA-7mqq-6cf9-v2qp lists affected ranges: RubyGems rack >=0 =3.0.0.beta1 =3.2.0 <3.2.6)

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