Rack: Multipart boundary ambiguity guard in Rack::Multipart::Parser can be bypassed with a quoted boundary value, allowing WAF bypass

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-125108
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-11-09 22:18:41 UTC
Updated2026-11-12 19:18:09 UTC
DescriptionRack is a modular Ruby web server interface. Prior to 2.2.25, 3.1.23, and 3.2.8, Rack::Multipart::Parser.parse_boundary can skip a leading empty or quoted boundary parameter in a multipart Content-Type header and accept a later parameter. Rack can therefore parse a request body with a boundary that a conforming intermediary would not derive, allowing form fields or file uploads to reach an application without the intended proxy or web application firewall inspection. This issue is fixed in versions 2.2.25, 3.1.23, and 3.2.8.

Risk And Classification

Primary CVSS: v3.1 3.7 LOW from [email protected]

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

Problem Types: CWE-436 | CWE-436 CWE-436: Interpretation Conflict

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary3.7LOWCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
3.1CNADECLARED3.7LOWCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
None

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Rack Rack affected < 2.2.25 Not specified
CNA Rack Rack affected >= 3.0, < 3.1.23 Not specified
CNA Rack Rack affected >= 3.2, < 3.2.8 Not specified

References

ReferenceSourceLinkTags
github.com/rack/rack/commit/19a1a19cb4da97d61c8d5effeb2e927c44370ae9 [email protected] github.com
github.com/rack/rack/releases/tag/v3.1.23 [email protected] github.com
github.com/rack/rack/releases/tag/v2.2.25 [email protected] github.com
github.com/rack/rack/security/advisories/GHSA-p8x9-v4hv-2w4g [email protected] github.com
github.com/rack/rack/commit/a29512324265790a5536b830490075d0d79323be [email protected] github.com
github.com/rack/rack/releases/tag/v3.2.8 [email protected] github.com
github.com/rack/rack/commit/d5e928b803da30b8e40171dbd4be39bed7daa6fa [email protected] github.com
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