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CVE-2025-61771— Rack's multipart parser buffers large non‑file fields entirely in memory, enabling DoS (memory exhaustion)

Quick assessment

Affected
rack rack
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Rack是Rack开源的一个模块化的Ruby web服务器界面。 Rack 2.2.19之前版本、3.1.17之前版本和3.2.2之前版本存在资源管理错误漏洞，该漏洞源于Rack::Multipart::Parser将非文件表单字段完全存储在内存中，可能导致内存耗尽和拒绝服务攻击。

CVSS 7.5 · High EPSS 0.56% · P45

Possible ATT&CK Techniques 1 AI

T1499 · Endpoint Denial of Service
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I. Basic Information for CVE-2025-61771

Vulnerability Information
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Vulnerability Title
Rack's multipart parser buffers large non‑file fields entirely in memory, enabling DoS (memory exhaustion)
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
未加控制的资源消耗(资源穷尽)
Source: CVE Program / CVE List V5
Vulnerability Title
Rack 资源管理错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Rack是Rack开源的一个模块化的Ruby web服务器界面。 Rack 2.2.19之前版本、3.1.17之前版本和3.2.2之前版本存在资源管理错误漏洞，该漏洞源于Rack::Multipart::Parser将非文件表单字段完全存储在内存中，可能导致内存耗尽和拒绝服务攻击。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
rack rack < 2.2.19 -

II. Public POCs for CVE-2025-61771

# POC Description Source Link Shenlong Link
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Qwen3.6-35B-A3B · 7440 chars
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III. Intelligence Information for CVE-2025-61771

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Patches & Fixes for CVE-2025-61771 (3)

Vendor Advisories for CVE-2025-61771 (1)

Same Patch Batch · rack · 2025-10-07 · 3 CVEs total

CVE-2025-61772 7.5 HIGH Rack's multipart parser buffers unbounded per-part headers, enabling DoS (memory exhaustio
CVE-2025-61770 7.5 HIGH Rack's unbounded multipart preamble buffering enables DoS (memory exhaustion)

IV. Related Vulnerabilities

Same product: rack
Same vendor: rack
Same weakness: CWE-400

V. Comments for CVE-2025-61771

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