CVE-2025-61771
Rack's multipart parser buffers large non‑file fields entirely in memory, enabling DoS (memory exhaustion)
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.
INFO
Published Date :
Oct. 7, 2025, 3:16 p.m.
Last Modified :
Oct. 10, 2025, 4:45 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | HIGH | [email protected] |
Solution
- Update Rack to version 2.2.19, 3.1.17, or 3.2.2.
- Restrict maximum request body size at proxy.
- Validate and reject large form fields in application.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2025-61771.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2025-61771 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2025-61771
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2025-61771 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2025-61771 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
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Initial Analysis by [email protected]
Oct. 10, 2025
Action Type Old Value New Value Added CPE Configuration OR *cpe:2.3:a:rack:rack:*:*:*:*:*:ruby:*:* versions up to (excluding) 2.2.19 *cpe:2.3:a:rack:rack:*:*:*:*:*:ruby:*:* versions from (including) 3.1.0 up to (excluding) 3.1.17 *cpe:2.3:a:rack:rack:*:*:*:*:*:ruby:*:* versions from (including) 3.2.0 up to (excluding) 3.2.2 Added Reference Type GitHub, Inc.: https://github.com/rack/rack/commit/589127f4ac8b5cf11cf88fb0cd116ffed4d2181e Types: Patch Added Reference Type GitHub, Inc.: https://github.com/rack/rack/commit/d869fed663b113b95a74ad53e1b5cae6ab31f29e Types: Patch Added Reference Type GitHub, Inc.: https://github.com/rack/rack/commit/e08f78c656c9394d6737c022bde087e0f33336fd Types: Patch Added Reference Type GitHub, Inc.: https://github.com/rack/rack/security/advisories/GHSA-w9pc-fmgc-vxvw Types: Vendor Advisory -
New CVE Received by [email protected]
Oct. 07, 2025
Action Type Old Value New Value Added 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. Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Added CWE CWE-400 Added Reference https://github.com/rack/rack/commit/589127f4ac8b5cf11cf88fb0cd116ffed4d2181e Added Reference https://github.com/rack/rack/commit/d869fed663b113b95a74ad53e1b5cae6ab31f29e Added Reference https://github.com/rack/rack/commit/e08f78c656c9394d6737c022bde087e0f33336fd Added Reference https://github.com/rack/rack/security/advisories/GHSA-w9pc-fmgc-vxvw