Rack's multipart parser buffers large non‑file fields entirely in memory, enabling DoS (memory exhaustion)
Summary
Rack's multipart parser buffers large non‑file fields entirely in memory, enabling DoS (memory exhaustion)
Original description
The description as published by the source.
Rack is a modular Ruby web server interface. In versions prior to 2.2.19, 3.1.17, and 3.2.2, ``Rack::Multipart::Parserstores non-file form fields (parts without afilename) entirely in memory as Ruby Stringobjects. 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., Nginxclient_max_body_size`) and validating and rejecting unusually large form fields at the application level.
Source: OSV.dev (Open Source Vulnerabilities) NVD GitHub Advisory OSV
Fix status by distribution
Fixed packages published by each distribution for this CVE
- Debian DEBIAN-CVE-2025-61771 ruby-rack Fixed in: 2.1.4-3+deb11u4
References
- advisory github.com
- advisory github.com
- advisory nvd.nist.gov
- patch github.com
- patch github.com
- patch github.com