REDHAT-BUG-2402200: Medium severity Rack Rack vulnerability

Published Oct 7, 2025
·
Updated

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 clientmaxbodysize).

Affected Software

1 affected component
Rack Rack<2.2.19, <3.1.17, <3.2.2

Remediation

Recommended actions to resolve this vulnerability, in priority order.

  1. Upgrade

    Upgrade Rack to a version that resolves this vulnerability.

    Fixed in 2.2.19
  2. Upgrade

    Upgrade Rack to a version that resolves this vulnerability.

    Fixed in 3.1.17
  3. Upgrade

    Upgrade Rack to a version that resolves this vulnerability.

    Fixed in 3.2.2
  4. Configuration

    As a workaround, restrict maximum request sizes at the proxy or web server layer (e.g., set Nginx `client_max_body_size`) to reduce the impact of large/incomplete multipart requests.

    Nginx (proxy/web server) client_max_body_size = <set to the maximum request size your application requires>

Event History

Oct 7, 2025
Data Sourced
via Red Hat·04:02 PM
DescriptionSeverityAffected Software

Frequently Asked Questions

1

What is the severity of REDHAT-BUG-2402200?

REDHAT-BUG-2402200 is classified as a high severity vulnerability due to the potential for unbounded memory consumption.

2

How do I fix REDHAT-BUG-2402200?

To fix REDHAT-BUG-2402200, upgrade Rack to version 2.2.19 or later, 3.1.17 or later, or 3.2.2 or later.

3

What are the affected versions in REDHAT-BUG-2402200?

Affected versions include Rack versions prior to 2.2.19, 3.1.17, and 3.2.2.

4

What does the vulnerability in REDHAT-BUG-2402200 allow?

The vulnerability allows unbounded data accumulation in memory when parsing multipart form data.

5

How can I determine if my application is affected by REDHAT-BUG-2402200?

Check the version of Rack your application is using and compare it against the affected versions specified in REDHAT-BUG-2402200.

Contact

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