CVE-2025-46727 | Unbounded-Parameter DoS in Rack::QueryParser

Rack is a modular Ruby web server interface. Prior to versions 2.2.14, 3.0.16, and 3.1.14, `Rack::QueryParser` parses query strings and `application/x-www-form-urlencoded` bodies into Ruby data structures without imposing any limit on the number of parameters, allowing attackers to send requests with extremely large numbers of parameters. The vulnerability arises because `Rack::QueryParser` iterates over each `&`-separated key-value pair and adds it to a Hash without enforcing an upper bound on the total number of parameters. This allows an attacker to send a single request containing hundreds of thousands (or more) of parameters, which consumes excessive memory and CPU during parsing. An attacker can trigger denial of service by sending specifically crafted HTTP requests, which can cause memory exhaustion or pin CPU resources, stalling or crashing the Rack server. This results in full service disruption until the affected worker is restarted. Versions 2.2.14, 3.0.16, and 3.1.14 fix the issue. Some other mitigations are available. One may use middleware to enforce a maximum query string size or parameter count, or employ a reverse proxy (such as Nginx) to limit request sizes and reject oversized query strings or bodies. Limiting request body sizes and query string lengths at the web server or CDN level is an effective mitigation.

Published: 2025-05-07 Last update: 2025-06-17 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2025-46727 is rated Moderate Risk (56.2/100): CVSS High severity, with medium exploitation likelihood (EPSS 0.81%). 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-2025-46727

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 2026-03-04 0.46% 0.81% +0.35%
2 2026-03-03 0.13% 0.46% +0.32%
3 2026-03-01 — 0.13% —

Full EPSS history (18 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2025-46727

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]
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-2025-46727

GitHub Security Advisory for CVE-2025-46727

GHSA-gjh7-p2fx-99vx · Severity: high · Ecosystem: rubygems — Rack has an Unbounded-Parameter DoS in Rack::QueryParser

OS Trackers for CVE-2025-46727

vendor priority summary link
debian not yet assigned CVE-2025-46727 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-2025-46727
redhat high — https://access.redhat.com/security/cve/CVE-2025-46727
suse high — https://www.suse.com/security/cve/CVE-2025-46727/
ubuntu medium CVE-2025-46727 medium priority: Ubuntu including 1 source packages (ruby-rack), 10 status rows across 10 suites (bionic, focal, jammy, noble, oracular, plucky, questing, trusty, upstream, xenial): released 7, ignored 3. https://ubuntu.com/security/CVE-2025-46727

Affected software / configurations for CVE-2025-46727

Vendor Product Version Raw CPE
rack rack < 2.2.14 cpe:2.3:a:rack:rack:*:*:*:*:*:ruby:*:*
rack rack >= 3.0.0, < 3.0.16 cpe:2.3:a:rack:rack:*:-:*:*:*:ruby:*:*
rack rack >= 3.1.0, < 3.1.14 cpe:2.3:a:rack:rack:*:-:*:*:*:ruby:*:*

References for CVE-2025-46727

cvelogic Threat Intelligence