CVE-2025-61772: rack DoS — Fix

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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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	< 2.2.19
rack	rack	3.1.0 — 3.1.17
rack	rack	3.2.0 — 3.2.2

References

Advisories & Patches

https://github.com/rack/rack/commit/589127f4ac8b5cf11cf88fb0cd116ffed4d2181e https://github.com/rack/rack/commit/d869fed663b113b95a74ad53e1b5cae6ab31f29e https://github.com/rack/rack/commit/e08f78c656c9394d6737c022bde087e0f33336fd https://github.com/rack/rack/security/advisories/GHSA-wpv5-97wm-hp9c

Frequently Asked Questions

What is CVE-2025-61772? +

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`). It has a CVSS v3.1 base score of 7.5 (HIGH).

How severe is CVE-2025-61772? +

CVE-2025-61772 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-2025-61772? +

CVE-2025-61772 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-2025-61772? +

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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