PT-2026-29817 · Rack · Rack

Th4S1S · Published 2026-04-02 · Updated 2026-04-02 · CVE-2026-34829

Mitre

CVSS v3.1

7.5

High

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

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.

Fix

Resource Exhaustion

Allocation of Resources Without Limits

Weakness Enumeration

CWE-400

CWE-770

Related Identifiers

CVE-2026-34829

Affected Products

Rack

References · 2

• https://nvd.nist.gov/vuln/detail/CVE-2026-34829 · Security Note
• https://github.com/rack/rack/security/advisories/GHSA-8vqr-qjwx-82mw · Note