CVE-2025-61772
Unknown Unknown - Not Provided
BaseFortify

Publication date: 2025-10-07

Last updated on: 2025-10-10

Assigner: GitHub, Inc.

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` can accumulate unbounded data when a multipart part’s header block never terminates with the required blank line (`CRLFCRLF`). The parser keeps appending incoming bytes to memory without a size cap, allowing a remote attacker to exhaust memory and cause a denial of service (DoS). Attackers can send incomplete multipart headers to trigger high memory use, leading to process termination (OOM) or severe slowdown. The effect scales with request size limits and concurrency. All applications handling multipart uploads may be affected. Versions 2.2.19, 3.1.17, and 3.2.2 cap per-part header size (e.g., 64 KiB). As a workaround, restrict maximum request sizes at the proxy or web server layer (e.g., Nginx `client_max_body_size`).
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Meta Information
Published
2025-10-07
Last Modified
2025-10-10
Generated
2026-05-07
AI Q&A
2025-10-07
EPSS Evaluated
2026-05-05
NVD
Affected Vendors & Products
Showing 3 associated CPEs
Vendor Product Version / Range
rack rack to 2.2.19 (exc)
rack rack From 3.1.0 (inc) to 3.1.17 (exc)
rack rack From 3.2.0 (inc) to 3.2.2 (exc)
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-400 The product does not properly control the allocation and maintenance of a limited resource.
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?

This vulnerability exists in the Rack Ruby web server interface where the multipart parser can accumulate unlimited data if a multipart part's header block never ends with the required blank line (CRLFCRLF). Because there is no size limit on the header data, an attacker can send incomplete multipart headers that cause the parser to keep appending data to memory without bounds, leading to excessive memory use.


How can this vulnerability impact me? :

The vulnerability can lead to a denial of service (DoS) by exhausting the server's memory. Attackers can cause the server process to run out of memory (OOM) or experience severe slowdowns by sending specially crafted incomplete multipart headers. The impact worsens with larger request sizes and higher concurrency, potentially causing application crashes or degraded performance.


What immediate steps should I take to mitigate this vulnerability?

To mitigate this vulnerability immediately, restrict maximum request sizes at the proxy or web server layer. For example, if using Nginx, set the 'client_max_body_size' directive to limit the size of incoming requests. Additionally, upgrade Rack to versions 2.2.19, 3.1.17, or 3.2.2 or later, which include a cap on per-part header size to prevent unbounded memory accumulation.


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