CVE-2025-61771

Publication date 7 October 2025

Last updated 15 January 2026

Ubuntu priority

Cvss 3 Severity Score

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.

Status

Show unmaintained releases

Package	Ubuntu Release	Status
ruby-rack	25.10 questing	Fixed 3.1.16-0.1ubuntu0.1
	25.04 plucky	Ignored end of life, was needed
	24.04 LTS noble	Fixed 2.2.7-1ubuntu0.5
	22.04 LTS jammy	Fixed 2.1.4-5ubuntu1.2
	20.04 LTS focal	Ignored changes too intrusive
	18.04 LTS bionic	Ignored changes too intrusive
	16.04 LTS xenial	Ignored end of ESM support, was ignored [changes too intrusive]
	14.04 LTS trusty	Ignored changes too intrusive

Patch details

For informational purposes only. We recommend not to cherry-pick updates. How can I get the fixes?

Package	Patch details
ruby-rack	Upstream: 3beacfc Upstream: f224f93 Upstream: c370dcd

Severity score breakdown

Parameter	Value
Base score	7.5 · High
Attack vector	Network
Attack complexity	Low
Privileges required	None
User interaction	None
Scope	Unchanged
Confidentiality	None
Integrity impact	None
Availability impact	High
Vector	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References

Related Ubuntu Security Notices (USN)

USN-7960-1
Rack vulnerabilities
14 January 2026