Rack up to 2.2.22/3.1.20/3.2.5 Regular Expression Rack::Directory permissive regular expression

Summaryinfo

A vulnerability, which was classified as problematic, has been found in Rack up to 2.2.22/3.1.20/3.2.5. The affected element is the function Rack::Directory of the component Regular Expression Handler. This manipulation causes permissive regular expression. This vulnerability appears as CVE-2026-34763. The attack may be initiated remotely. There is no available exploit. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability classified as problematic was found in Rack up to 2.2.22/3.1.20/3.2.5. Affected by this vulnerability is the function Rack::Directory of the component Regular Expression Handler. The manipulation with an unknown input leads to a permissive regular expression vulnerability. The CWE definition for the vulnerability is CWE-625. The product uses a regular expression that does not sufficiently restrict the set of allowed values. As an impact it is known to affect confidentiality. The summary by CVE is:

Rack 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.

It is possible to read the advisory at github.com. This vulnerability is known as CVE-2026-34763 since 03/30/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. Technical details of the vulnerability are known, but there is no available exploit.

The vulnerability scanner Nessus provides a plugin with the ID 304833 (Linux Distros Unpatched Vulnerability : CVE-2026-34763), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 2.2.23, 3.1.21 or 3.2.6 eliminates this vulnerability.

The vulnerability is also documented in the databases at Tenable (304833) and CERT Bund (WID-SEC-2026-1687). Be aware that VulDB is the high quality source for vulnerability data.

Affected

• IBM License Metric Tool

Productinfo

Name

• Rack

Version

• 2.2.0
• 2.2.1
• 2.2.2
• 2.2.3
• 2.2.4
• 2.2.5
• 2.2.6
• 2.2.7
• 2.2.8
• 2.2.9
• 2.2.10
• 2.2.11
• 2.2.12
• 2.2.13
• 2.2.14
• 2.2.15
• 2.2.16
• 2.2.17
• 2.2.18
• 2.2.19
• 2.2.20
• 2.2.21
• 2.2.22
• 3.1.0
• 3.1.1
• 3.1.2
• 3.1.3
• 3.1.4
• 3.1.5
• 3.1.6
• 3.1.7
• 3.1.8
• 3.1.9
• 3.1.10
• 3.1.11
• 3.1.12
• 3.1.13
• 3.1.14
• 3.1.15
• 3.1.16
• 3.1.17
• 3.1.18
• 3.1.19
• 3.1.20
• 3.2.0
• 3.2.1
• 3.2.2
• 3.2.3
• 3.2.4
• 3.2.5

Website

• Product: https://github.com/rack/rack/

CPE 2.3info

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CPE 2.2info

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Be aware that VulDB is the high quality source for vulnerability data.

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