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High severity7.5NVD Advisory· Published Apr 2, 2026· Updated Apr 16, 2026

CVE-2026-34829

CVE-2026-34829

Description

Rack is a modular Ruby web server interface. Prior to versions 2.2.23, 3.1.21, and 3.2.6, Rack::Multipart::Parser only wraps the request body in a BoundedIO when CONTENT_LENGTH is present. When a multipart/form-data request is sent without a Content-Length header, such as with HTTP chunked transfer encoding, multipart parsing continues until end-of-stream with no total size limit. For file parts, the uploaded body is written directly to a temporary file on disk rather than being constrained by the buffered in-memory upload limit. An unauthenticated attacker can therefore stream an arbitrarily large multipart file upload and consume unbounded disk space. This results in a denial of service condition for Rack applications that accept multipart form data. This issue has been patched in versions 2.2.23, 3.1.21, and 3.2.6.

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Affected packages

Versions sourced from the GitHub Security Advisory.

PackageAffected versionsPatched versions
rackRubyGems
< 2.2.232.2.23
rackRubyGems
>= 3.0.0.beta1, < 3.1.213.1.21
rackRubyGems
>= 3.2.0, < 3.2.63.2.6

Affected products

65

Patches

Vulnerability mechanics

References

4

News mentions

0

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