Resource exhaustion in Rack
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`).
Vulnerability class: DoS (Denial of Service)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
EPSS exploit prediction
EPSS: 0.006 (49.2th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 49th percentile — 49.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.006 · newest: 0.006 · change: +0.000
Affected products
- Rack — versions < 2.2.20, >= 3.0, < 3.1.18, >= 3.2, < 3.2.3
Weakness classification (CWE)
References
- github.com/rack/rack/security/advisories/GHSA-6xw4-3v39-52mm (Third Party Advisory, Mitigation)
- github.com/rack/rack/commit/4e2c903991a790ee211a3021808ff4fd6fe82881 (Patch)
- github.com/rack/rack/commit/cbd541e8a3d0c5830a3c9a30d3718ce2e124f9db (Patch)
- github.com/rack/rack/commit/e179614c4a653283286f5f046428cbb85f21146f (Patch)
Frequently asked questions
- What is CVE-2025-61919?
- CVE-2025-61919 is a high-severity vulnerability in Rack, classified under Uncontrolled Resource Consumption. CVSS score: 7.5/10. Published 2025-10-10.
- How severe is CVE-2025-61919?
- High severity. CVSS v3 base score is 7.5 out of 10.