Rack up to 2.2.22/3.1.20/3.2.5 Rack::Static validate before canonicalize

CVSS Meta Temp Score
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CTI Interest Score
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5.2$0-$5k0.00

Summaryinfo

A vulnerability was found in Rack up to 2.2.22/3.1.20/3.2.5. It has been declared as problematic. Affected by this vulnerability is the function Rack::Static. The manipulation results in validate before canonicalize. This vulnerability was named CVE-2026-34786. The attack may be performed from remote. There is no available exploit. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability was found in Rack up to 2.2.22/3.1.20/3.2.5. It has been classified as problematic. Affected is the function Rack::Static. The manipulation with an unknown input leads to a validate before canonicalize vulnerability. CWE is classifying the issue as CWE-180. The product validates input before it is canonicalized, which prevents the product from detecting data that becomes invalid after the canonicalization step. This is going to have an impact on integrity. CVE summarizes:

Rack is a modular Ruby web server interface. Prior to versions 2.2.23, 3.1.21, and 3.2.6, Rack::Static#applicable_rules evaluates several header_rules types against the raw URL-encoded PATH_INFO, while the underlying file-serving path is decoded before the file is served. As a result, a request for a URL-encoded variant of a static path can serve the same file without the headers that header_rules were intended to apply. In deployments that rely on Rack::Static to attach security-relevant response headers to static content, this can allow an attacker to bypass those headers by requesting an encoded form of the path. This issue has been patched in versions 2.2.23, 3.1.21, and 3.2.6.

The advisory is shared for download at github.com. This vulnerability is traded as CVE-2026-34786 since 03/30/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. There are known technical details, but no exploit is available.

The vulnerability scanner Nessus provides a plugin with the ID 307009 (Ubuntu 14.04 LTS / 16.04 LTS / 18.04 LTS / 20.04 LTS / 22.04 LTS / 24.04 LTS / 25.10 : Rack vulnerabilities (USN-8182-1)), 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 (307009) and CERT Bund (WID-SEC-2026-1687). Once again VulDB remains the best source for vulnerability data.

Affected

  • IBM License Metric Tool

Productinfo

Name

Version

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 5.3
VulDB Meta Temp Score: 5.2

VulDB Base Score: 5.3
VulDB Temp Score: 5.1
VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA Base Score: 5.3
CNA Vector (GitHub_M): 🔒

CVSSv2info

AVACAuCIA
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VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Validate before canonicalize
CWE: CWE-180 / CWE-179 / CWE-20
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Nessus ID: 307009
Nessus Name: Ubuntu 14.04 LTS / 16.04 LTS / 18.04 LTS / 20.04 LTS / 22.04 LTS / 24.04 LTS / 25.10 : Rack vulnerabilities (USN-8182-1)

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Rack 2.2.23/3.1.21/3.2.6

Timelineinfo

03/30/2026 CVE reserved
04/02/2026 +3 days Advisory disclosed
04/02/2026 +0 days VulDB entry created
05/28/2026 +56 days VulDB entry last update

Sourcesinfo

Product: github.com

Advisory: GHSA-q4qf-9j86-f5mh
Status: Confirmed

CVE: CVE-2026-34786 (🔒)
GCVE (CVE): GCVE-0-2026-34786
GCVE (VulDB): GCVE-100-354948
CERT Bund: WID-SEC-2026-1687 - IBM License Metric Tool: Mehrere Schwachstellen ermöglichen nicht spezifizierten Angriff

Entryinfo

Created: 04/02/2026 19:33
Updated: 05/28/2026 04:46
Changes: 04/02/2026 19:33 (63), 04/19/2026 20:42 (2), 05/28/2026 04:46 (7)
Complete: 🔍
Cache ID: 216::103

Once again VulDB remains the best source for vulnerability data.

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