CVE-2025-59830 | Rack QueryParser has an unsafe default allowing params_limit bypass via semicolon-separated parameters

Rack is a modular Ruby web server interface. Prior to version 2.2.18, Rack::QueryParser enforces its params_limit only for parameters separated by &, while still splitting on both & and ;. As a result, attackers could use ; separators to bypass the parameter count limit and submit more parameters than intended. Applications or middleware that directly invoke Rack::QueryParser with its default configuration (no explicit delimiter) could be exposed to increased CPU and memory consumption. This can be abused as a limited denial-of-service vector. This issue has been patched in version 2.2.18.

Published: 2025-09-25 Last update: 2025-10-10 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2025-59830 is rated Low Risk (35.7/100): CVSS High severity, with low exploitation likelihood (EPSS 0.05%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

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-2025-59830

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 2025-10-01 0.04% 0.05% +0.01%
2 2025-09-26 — 0.04% —

Full EPSS history (2 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2025-59830

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-2025-59830

GitHub Security Advisory for CVE-2025-59830

GHSA-625h-95r8-8xpm · Severity: high · Ecosystem: rubygems — Rack has an unsafe default in Rack::QueryParser allows params_limit bypass via semicolon-separated parameters

OS Trackers for CVE-2025-59830

vendor priority summary link
debian not yet assigned CVE-2025-59830 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-2025-59830
redhat medium — https://access.redhat.com/security/cve/CVE-2025-59830
suse high — https://www.suse.com/security/cve/CVE-2025-59830/
ubuntu medium CVE-2025-59830 medium priority: Ubuntu including 1 source packages (ruby-rack), 9 status rows across 9 suites (bionic, focal, jammy, noble, plucky, questing, trusty, upstream, xenial): released 5, ignored 3, not-affected 1. https://ubuntu.com/security/CVE-2025-59830

Affected software / configurations for CVE-2025-59830

Vendor Product Version Raw CPE
rack rack < 2.2.18 cpe:2.3:a:rack:rack:*:*:*:*:*:ruby:*:*

References for CVE-2025-59830

cvelogic Threat Intelligence