cbcvebase.
CVE-2026-34827
published 2026-04-02

CVE-2026-34827: Rack is a modular Ruby web server interface. From versions 3.0.0.beta1 to before 3.1.21, and 3.2.0 to before 3.2.6, Rack::Multipart::Parser#handle_mime_head…

PriorityP346high7.5CVSS 3.1
AVNACLPRNUINSUCNINAH
EPSS
0.47%
37.5th percentile
Rack is a modular Ruby web server interface. From versions 3.0.0.beta1 to before 3.1.21, and 3.2.0 to before 3.2.6, Rack::Multipart::Parser#handle_mime_head parses quoted multipart parameters such as Content-Disposition: form-data; name="..." using repeated String#index searches combined with String#slice! prefix deletion. For escape-heavy quoted values, this causes super-linear processing. An unauthenticated attacker can send a crafted multipart/form-data request containing many parts with long backslash-escaped parameter values to trigger excessive CPU usage during multipart parsing. This results in a denial of service condition in Rack applications that accept multipart form data. This issue has been patched in versions 3.1.21 and 3.2.6.

Affected

7 ranges
VendorProductVersion rangeFixed in
debianruby-rack< ruby-rack 3.2.6-2 (sid)ruby-rack 3.2.6-2 (sid)
rackrack
rackrack
rackrack>= 3.0.0 < 3.1.213.1.21
rackrack>= 3.0.0.beta1 < 3.1.213.1.21
rackrack>= 3.2.0 < 3.2.63.2.6
rackrack>= 3.2.0 < 3.2.63.2.6

CVSS provenance

nvdv3.17.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
osv7.5HIGH
vendor_debian7.5HIGH
vendor_redhat7.5HIGH
vendor_ubuntu3.7LOW
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