CVE-2026-34829

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.

Affected products

Linuxmint, Rack, Red Os, Ubuntu

Rack

< 2.2.23, 3.1.21, 3.2.6

Fix

Available

CVSS 3.1

7.5 HIGH

EPSS

0.4% (30th percentile)

Weakness

CWE-400, CWE-770

NVD status

Modified

Published

2026-04-02

No exploit for CVE-2026-34829 has been indexed yet. Our index is built from live traffic and upstream syncs, so this page can only say what it knows — not that no exploit exists.