CVE-2025-61771
Rack's multipart parser buffers large non‑file fields entirely in memory, enabling DoS (memory exhaustion)
- Published
- Updated
- Reserved
- Assigned by
- GitHub_M
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.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| GitHub_MCNA (assigner) | 3.1 | High7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
| NVDNVD · Analyzed | 3.1 | High7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
- EPSS (exploitation in 30 days)
- 0.56% · top 53% of all CVEs (6 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: yes · Technical impact: partial
The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.5.
Weakness
Affected products
Affected packages
From reviewed advisories of the GitHub Advisory Database.
- RubyGemsrackGHSA-w9pc-fmgc-vxvw (opens in a new tab)
References (4)
- https://github.com/rack/rack/security/advisories/GHSA-w9pc-fmgc-vxvw (opens in a new tab)x_refsource_CONFIRM
- https://github.com/rack/rack/commit/589127f4ac8b5cf11cf88fb0cd116ffed4d2181e (opens in a new tab)x_refsource_MISC
- https://github.com/rack/rack/commit/d869fed663b113b95a74ad53e1b5cae6ab31f29e (opens in a new tab)x_refsource_MISC
- https://github.com/rack/rack/commit/e08f78c656c9394d6737c022bde087e0f33336fd (opens in a new tab)x_refsource_MISC
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisory GHSA-w9pc-fmgc-vxvw (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://trackcve.app/cve/CVE-2025-61771)Record last updated .