CVE-2025-61771
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.
- CVSS 3.1
- 7.5
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - EPSS
- 0.6% chance of exploitation in the next 30 days; higher than 46% of CVEs (scores of 2026-10-25)
- CWE
- CWE-400
- Published
- Modified
- Record from
- the NVD, synced
Affected
- rack:rack
Packages (OSV)
| Advisory | Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|---|
| GHSA-w9pc-fmgc-vxvw | RubyGems | rack | <2.2.19 | 2.2.19 |
| GHSA-w9pc-fmgc-vxvw | RubyGems | rack | >=3.1 <3.1.17 | 3.1.17 |
| GHSA-w9pc-fmgc-vxvw | RubyGems | rack | >=3.2 <3.2.2 | 3.2.2 |