Rack is a modular Ruby web server interface. In versions prior to 2.2.19, 3.1.17, and 3.2.2, ``Rack::Multipart::Parser` stores non-file form fields (parts without a `filename`) entirely in memory as Ruby `String` objects. A single large text field in a multipart/form-data request (hundreds of megabytes or more) can consume equivalent process memory, potentially leading to out-of-memory (OOM) conditions and denial of service (DoS). Attackers can send large non-file fields to trigger excessive memory usage. Impact scales with request size and concurrency, potentially leading to worker crashes or severe garbage-collection overhead. All Rack applications processing multipart form submissions are affected. Versions 2.2.19, 3.1.17, and 3.2.2 enforce a reasonable size cap for non-file fields (e.g., 2 MiB). Workarounds include restricting maximum request body size at the web-server or proxy layer (e.g., Nginx `client_max_body_size`) and validating and rejecting unusually large form fields at the application level.
Advisories
Source ID Title
Github GHSA Github GHSA GHSA-w9pc-fmgc-vxvw Rack: Multipart parser buffers large non‑file fields entirely in memory, enabling DoS (memory exhaustion)
Fixes

Solution

No solution given by the vendor.


Workaround

No workaround given by the vendor.

History

Wed, 08 Oct 2025 13:45:00 +0000

Type Values Removed Values Added
First Time appeared Rack
Rack rack
Vendors & Products Rack
Rack rack

Tue, 07 Oct 2025 18:15:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Tue, 07 Oct 2025 15:00:00 +0000

Type Values Removed Values Added
Description Rack is a modular Ruby web server interface. In versions prior to 2.2.19, 3.1.17, and 3.2.2, ``Rack::Multipart::Parser` stores non-file form fields (parts without a `filename`) entirely in memory as Ruby `String` objects. A single large text field in a multipart/form-data request (hundreds of megabytes or more) can consume equivalent process memory, potentially leading to out-of-memory (OOM) conditions and denial of service (DoS). Attackers can send large non-file fields to trigger excessive memory usage. Impact scales with request size and concurrency, potentially leading to worker crashes or severe garbage-collection overhead. All Rack applications processing multipart form submissions are affected. Versions 2.2.19, 3.1.17, and 3.2.2 enforce a reasonable size cap for non-file fields (e.g., 2 MiB). Workarounds include restricting maximum request body size at the web-server or proxy layer (e.g., Nginx `client_max_body_size`) and validating and rejecting unusually large form fields at the application level.
Title Rack's multipart parser buffers large non‑file fields entirely in memory, enabling DoS (memory exhaustion)
Weaknesses CWE-400
References
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}


cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2025-10-07T17:52:09.399Z

Reserved: 2025-09-30T19:43:49.900Z

Link: CVE-2025-61771

cve-icon Vulnrichment

Updated: 2025-10-07T17:52:01.550Z

cve-icon NVD

Status : Awaiting Analysis

Published: 2025-10-07T15:16:03.123

Modified: 2025-10-08T19:38:32.610

Link: CVE-2025-61771

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2025-10-08T13:36:33Z