CVE-2025-61770

Published Oct 7, 2025

Last updated a year ago

CVSS high 7.5
Rails

Overview

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` buffers the entire multipart preamble (bytes before the first boundary) in memory without any size limit. A client can send a large preamble followed by a valid boundary, causing significant memory use and potential process termination due to out-of-memory (OOM) conditions. Remote attackers can trigger large transient memory spikes by including a long preamble in multipart/form-data requests. The impact scales with allowed request sizes and concurrency, potentially causing worker crashes or severe slowdown due to garbage collection. Versions 2.2.19, 3.1.17, and 3.2.2 enforce a preamble size limit (e.g., 16 KiB) or discard preamble data entirely. Workarounds include limiting total request body size at the proxy or web server level and monitoring memory and set per-process limits to prevent OOM conditions.
Source
security-advisories@github.com
NVD status
Analyzed
Products
rack

Risk scores

CVSS 3.1

Type
Secondary
Base score
7.5
Impact score
3.6
Exploitability score
3.9
Vector string
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Severity
HIGH

Weaknesses

security-advisories@github.com
CWE-400

Social media

Hype score
Not currently trending

  1. Rack's unbounded multipart preamble buffering enables DoS (memory exhaustion) · CVE-2025-61770 · GitHub Advisory Database https://t.co/pythYS9rzy

    @pHo9UBenaA

    9 Oct 2025

    30 Impressions

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  2. CVE-2025-61770 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` buffers the entire multipart preamble (bytes be… https://t.co/eeObdSZkNV

    @CVEnew

    7 Oct 2025

    100 Impressions

    0 Retweets

    1 Like

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Configurations

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References

Sources include official advisories and independent security research.