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Vulnerability Details :

CVE-2026-34786

Summary
Assigner-GitHub_M
Assigner Org ID-a0819718-46f1-4df5-94e2-005712e83aaa
Published At-02 Apr, 2026 | 16:44
Updated At-03 Apr, 2026 | 17:38
Rejected At-
Credits

Rack: Rack::Static header_rules bypass via URL-encoded paths

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.

Vendors
-
Not available
Products
-
Metrics (CVSS)
VersionBase scoreBase severityVector
Weaknesses
Attack Patterns
Solution/Workaround
References
HyperlinkResource Type
EPSS History
Score
Latest Score
-
N/A
No data available for selected date range
Percentile
Latest Percentile
-
N/A
No data available for selected date range
Stakeholder-Specific Vulnerability Categorization (SSVC)
▼Common Vulnerabilities and Exposures (CVE)
cve.org
Assigner:GitHub_M
Assigner Org ID:a0819718-46f1-4df5-94e2-005712e83aaa
Published At:02 Apr, 2026 | 16:44
Updated At:03 Apr, 2026 | 17:38
Rejected At:
▼CVE Numbering Authority (CNA)
Rack: Rack::Static header_rules bypass via URL-encoded paths

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.

Affected Products
Vendor
rack
Product
rack
Versions
Affected
  • < 2.2.23
  • >= 3.0.0.beta1, < 3.1.21
  • >= 3.2.0, < 3.2.6
Problem Types
TypeCWE IDDescription
CWECWE-180CWE-180: Incorrect Behavior Order: Validate Before Canonicalize
Type: CWE
CWE ID: CWE-180
Description: CWE-180: Incorrect Behavior Order: Validate Before Canonicalize
Metrics
VersionBase scoreBase severityVector
3.15.3MEDIUM
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
Version: 3.1
Base score: 5.3
Base severity: MEDIUM
Vector:
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
Metrics Other Info
Impacts
CAPEC IDDescription
Solutions
Configurations
Workarounds
Exploits
Credits
Timeline
EventDate
Replaced By
Rejected Reason
References
HyperlinkResource
https://github.com/rack/rack/security/advisories/GHSA-q4qf-9j86-f5mh
x_refsource_CONFIRM
Hyperlink: https://github.com/rack/rack/security/advisories/GHSA-q4qf-9j86-f5mh
Resource:
x_refsource_CONFIRM
▼Authorized Data Publishers (ADP)
CISA ADP Vulnrichment
Affected Products
Metrics
VersionBase scoreBase severityVector
Metrics Other Info
Impacts
CAPEC IDDescription
Solutions
Configurations
Workarounds
Exploits
Credits
Timeline
EventDate
Replaced By
Rejected Reason
References
HyperlinkResource
Information is not available yet
▼National Vulnerability Database (NVD)
nvd.nist.gov
Source:security-advisories@github.com
Published At:02 Apr, 2026 | 17:16
Updated At:16 Apr, 2026 | 17:19

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.

CISA Catalog
Date AddedDue DateVulnerability NameRequired Action
N/A
Date Added: N/A
Due Date: N/A
Vulnerability Name: N/A
Required Action: N/A
Metrics
TypeVersionBase scoreBase severityVector
Secondary3.15.3MEDIUM
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
Type: Secondary
Version: 3.1
Base score: 5.3
Base severity: MEDIUM
Vector:
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
CPE Matches
rack
rack
>>rack>>Versions before 2.2.23(exclusive)
cpe:2.3:a:rack:rack:*:*:*:*:*:ruby:*:*
rack
rack
>>rack>>Versions from 3.0.0(inclusive) to 3.1.21(exclusive)
cpe:2.3:a:rack:rack:*:*:*:*:*:ruby:*:*
rack
rack
>>rack>>Versions from 3.2.0(inclusive) to 3.2.6(exclusive)
cpe:2.3:a:rack:rack:*:*:*:*:*:ruby:*:*
Weaknesses
CWE IDTypeSource
CWE-180Primarysecurity-advisories@github.com
CWE ID: CWE-180
Type: Primary
Source: security-advisories@github.com
Evaluator Description
Evaluator Impact

Evaluator Solution

Vendor Statements
References
HyperlinkSourceResource
https://github.com/rack/rack/security/advisories/GHSA-q4qf-9j86-f5mhsecurity-advisories@github.com
Vendor Advisory
Hyperlink: https://github.com/rack/rack/security/advisories/GHSA-q4qf-9j86-f5mh
Source: security-advisories@github.com
Resource:
Vendor Advisory

Change History

0
Information is not available yet

Similar CVEs

1Records found
CVE-2026-26961
Matching Score-8
Assigner-GitHub, Inc.
ShareView Details
Matching Score-8
Assigner-GitHub, Inc.
CVSS Score-3.7||LOW
EPSS-0.01% / 2.85%
||
7 Day CHG~0.00%
Published-02 Apr, 2026 | 16:42
Updated-16 Apr, 2026 | 17:33
Rejected-Not Available
Known To Be Used In Ransomware Campaigns?-Not Available
KEV Added-Not Available
KEV Action Due Date-Not Available
Rack: Multipart Boundary Parsing Ambiguity allowing WAF Bypass

Rack is a modular Ruby web server interface. Prior to versions 2.2.23, 3.1.21, and 3.2.6, Rack::Multipart::Parser extracts the boundary parameter from multipart/form-data using a greedy regular expression. When a Content-Type header contains multiple boundary parameters, Rack selects the last one rather than the first. In deployments where an upstream proxy, WAF, or intermediary interprets the first boundary parameter, this mismatch can allow an attacker to smuggle multipart content past upstream inspection and have Rack parse a different body structure than the intermediary validated. This issue has been patched in versions 2.2.23, 3.1.21, and 3.2.6.

Action-Not Available
Vendor-rackrack
Product-rackrack
CWE ID-CWE-436
Interpretation Conflict
Details not found