Описание
Rack: Multipart parser buffers large non‑file fields entirely in memory, enabling DoS (memory exhaustion)
Summary
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).
Details
During multipart parsing, file parts are streamed to temporary files, but non-file parts are buffered into memory:
There is no size limit on these in-memory buffers. As a result, any large text field—while technically valid—will be loaded fully into process memory before being added to params.
Impact
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.
Mitigation
- Upgrade: Use a patched version of Rack that enforces a reasonable size cap for non-file fields (e.g., 2 MiB).
- Workarounds:
- Restrict maximum request body size at the web-server or proxy layer (e.g., Nginx
client_max_body_size). - Validate and reject unusually large form fields at the application level.
- Restrict maximum request body size at the web-server or proxy layer (e.g., Nginx
Ссылки
- https://github.com/rack/rack/security/advisories/GHSA-w9pc-fmgc-vxvw
- https://nvd.nist.gov/vuln/detail/CVE-2025-61771
- https://github.com/rack/rack/commit/589127f4ac8b5cf11cf88fb0cd116ffed4d2181e
- https://github.com/rack/rack/commit/d869fed663b113b95a74ad53e1b5cae6ab31f29e
- https://github.com/rack/rack/commit/e08f78c656c9394d6737c022bde087e0f33336fd
- https://github.com/rubysec/ruby-advisory-db/blob/master/gems/rack/CVE-2025-61771.yml
Пакеты
rack
< 2.2.19
2.2.19
rack
>= 3.1, < 3.1.17
3.1.17
rack
>= 3.2, < 3.2.2
3.2.2
Связанные уязвимости
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 a...
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 t
Rack is a modular Ruby web server interface. In versions prior to 2.2. ...
Уязвимость класса Rack::Multipart::Parser модульного интерфейса между веб-серверами и веб-приложениями Rack, позволяющая нарушителю вызвать отказ в обслуживании
