CVE-2025-61771: rack Uncontrolled Resource Consumption

Vulnerability summary

CVE-2025-61771 is a high (CVSS 7.5) Uncontrolled Resource Consumption vulnerability in rack. EPSS estimates a 0.56% chance of exploitation in the next 30 days, higher than 45.4% of scored vulnerabilities.

Timeline

1. 07-10-2025
   PublishedVulnerability first disclosed.
2. 07-10-2025
   Last modifiedVulnerability information updated.

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.

• CWE-400Uncontrolled Resource ConsumptionThe product does not properly control the allocation and maintenance of a limited resource.