CVE-2025-61919: rack DoS — Fix

Description

Rack is a modular Ruby web server interface. Prior to versions 2.2.20, 3.1.18, and 3.2.3, `Rack::Request#POST` reads the entire request body into memory for `Content-Type: application/x-www-form-urlencoded`, calling `rack.input.read(nil)` without enforcing a length or cap. Large request bodies can therefore be buffered completely into process memory before parsing, leading to denial of service (DoS) through memory exhaustion. Users should upgrade to Rack version 2.2.20, 3.1.18, or 3.2.3, anu of which enforces form parameter limits using `query_parser.bytesize_limit`, preventing unbounded reads of `application/x-www-form-urlencoded` bodies. Additionally, enforce strict maximum body size at the proxy or web server layer (e.g., Nginx `client_max_body_size`, Apache `LimitRequestBody`).

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CVSS v3.1 Score

7.5

HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Weakness Type (CWE)

CWE-400 Uncontrolled Resource Consumption

Affected Products

Vendor	Product	Versions
rack	rack	< 2.2.20
rack	rack	3.0.0 — 3.1.18
rack	rack	3.2.0 — 3.2.3

References

Advisories & Patches

https://github.com/rack/rack/commit/4e2c903991a790ee211a3021808ff4fd6fe82881 https://github.com/rack/rack/commit/cbd541e8a3d0c5830a3c9a30d3718ce2e124f9db https://github.com/rack/rack/commit/e179614c4a653283286f5f046428cbb85f21146f

Other References

https://github.com/rack/rack/security/advisories/GHSA-6xw4-3v39-52mm

Frequently Asked Questions

What is CVE-2025-61919? +

Rack is a modular Ruby web server interface. Prior to versions 2.2.20, 3.1.18, and 3.2.3, `Rack::Request#POST` reads the entire request body into memory for `Content-Type: application/x-www-form-urlencoded`, calling `rack.input.read(nil)` without enforcing a length or cap. Large request bodies can therefore be buffered completely into process memory before parsing, leading to denial of service (DoS) through memory exhaustion. Users should upgrade to Rack version 2.2.20, 3.1.18, or 3.2.3, anu of which enforces form parameter limits using `query_parser.bytesize_limit`, preventing unbounded reads of `application/x-www-form-urlencoded` bodies. Additionally, enforce strict maximum body size at the proxy or web server layer (e.g., Nginx `client_max_body_size`, Apache `LimitRequestBody`). It has a CVSS v3.1 base score of 7.5 (HIGH).

How severe is CVE-2025-61919? +

CVE-2025-61919 has a CVSS v3.1 score of 7.5 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching.

What products are affected by CVE-2025-61919? +

CVE-2025-61919 affects products from rack, specifically: rack. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2025-61919? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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