CVE-2025-61919 | Rack is vulnerable to a memory-exhaustion DoS through unbounded URL-encoded body parsing

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`).

Published: 2025-10-10 Last update: 2025-11-03 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2025-61919 is rated Moderate Risk (48.5/100): CVSS High severity, with medium exploitation likelihood (EPSS 0.29%). Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2025-61919

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-05-06 0.22% 0.29% +0.07%
2 2026-03-20 0.15% 0.22% +0.07%
3 2026-03-09 — 0.15% —

Full EPSS history (5 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2025-61919

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 3.6 [email protected]

Weakness enumeration for CVE-2025-61919

GitHub Security Advisory for CVE-2025-61919

GHSA-6xw4-3v39-52mm · Severity: high · Ecosystem: rubygems — Rack is vulnerable to a memory-exhaustion DoS through unbounded URL-encoded body parsing

OS Trackers for CVE-2025-61919

vendor priority summary link
debian not yet assigned CVE-2025-61919 not yet assigned priority: Debian including 1 source packages (ruby-rack), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2025-61919
redhat high — https://access.redhat.com/security/cve/CVE-2025-61919
suse high CVE-2025-61919 severity important: SUSE including 243 source package names (amazon/suse-sles-15-sp1-chost-byos-v20210304-hvm-ssd-x86_64, amazon/suse-sles-15-sp1-chost-byos-v20220127-hvm-ssd-x86_64, …), 367 product×package rows across 104 product lines (Image SL-Micro-Azure, Image SL-Micro-BYOS-Azure, … (104 product lines)): Known Affected 231, Fixed 128, Known Not Affected 8. https://www.suse.com/security/cve/CVE-2025-61919/
ubuntu medium CVE-2025-61919 medium priority: Ubuntu including 1 source packages (ruby-rack), 9 status rows across 9 suites (bionic, focal, jammy, noble, plucky, questing, trusty, upstream, xenial): ignored 4, released 4, needs-triage 1. https://ubuntu.com/security/CVE-2025-61919

Affected software / configurations for CVE-2025-61919

Vendor Product Version Raw CPE
rack rack < 2.2.20 cpe:2.3:a:rack:rack:*:*:*:*:*:ruby:*:*
rack rack >= 3.0.0, < 3.1.18 cpe:2.3:a:rack:rack:*:*:*:*:*:ruby:*:*
rack rack >= 3.2.0, < 3.2.3 cpe:2.3:a:rack:rack:*:*:*:*:*:ruby:*:*

References for CVE-2025-61919

cvelogic Threat Intelligence