CVE-2026-125108
Rack: Multipart boundary ambiguity guard in Rack::Multipart::Parser can be bypassed with a quoted boundary value, allowing WAF bypass
CVSS Score
3.7
EPSS Score
0.0%
EPSS Percentile
0th
Rack 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.
| CWE | CWE-436 |
| Vendor | rack |
| Product | rack |
| Published | Nov 9, 2026 |
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CVSS v3 Breakdown
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
None
Affected Versions
rack / rack
< 2.2.25 >= 3.0, < 3.1.23 >= 3.2, < 3.2.8
References
github.com: https://github.com/rack/rack/security/advisories/GHSA-p8x9-v4hv-2w4g github.com: https://github.com/rack/rack/commit/19a1a19cb4da97d61c8d5effeb2e927c44370ae9 github.com: https://github.com/rack/rack/commit/a29512324265790a5536b830490075d0d79323be github.com: https://github.com/rack/rack/commit/d5e928b803da30b8e40171dbd4be39bed7daa6fa github.com: https://github.com/rack/rack/releases/tag/v2.2.25 github.com: https://github.com/rack/rack/releases/tag/v3.1.23 github.com: https://github.com/rack/rack/releases/tag/v3.2.8