CVE-2018-16471

There is a possible XSS vulnerability in Rack before 2.0.6 and 1.6.11. Carefully crafted requests can impact the data returned by the `scheme` method on `Rack::Request`. Applications that expect the scheme to be limited to 'http' or 'https' and do not escape the return value could be vulnerable to an XSS attack. Note that applications using the normal escaping mechanisms provided by Rails may not impacted, but applications that bypass the escaping mechanisms, or do not use them may be vulnerable.

Published: 2018-11-13 Last update: 2026-06-16 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2018-16471 is rated Moderate Risk (51.9/100): CVSS Medium severity, with medium exploitation likelihood (EPSS 1.82%). 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-2018-16471

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 2026-06-15 0.83% 1.82% +0.99%
2 2026-04-20 0.30% 0.83% +0.53%
3 2026-03-26 — 0.30% —

Full EPSS history (51 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2018-16471

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
6.1 3.0 MEDIUM
CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N 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:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:L)
Some sensitive info could get out, but not a total data dump.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:N)
Service keeps running; no real outage angle.
 2.8 2.7 [email protected]
4.3 2.0 MEDIUM
AV:N/AC:M/Au:N/C:N/I:P/A:N Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:M)
Exploitation needs some favorable conditions, but not exceptional ones.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:N)
No availability impact.
 8.6 2.9 [email protected]

Weakness enumeration for CVE-2018-16471

GitHub Security Advisory for CVE-2018-16471

GHSA-5r2p-j47h-mhpg · Severity: medium · Ecosystem: rubygems — Rack vulnerable to Cross-site Scripting

OS Trackers for CVE-2018-16471

vendor priority summary link
debian not yet assigned CVE-2018-16471 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-2018-16471
redhat medium — https://access.redhat.com/security/cve/CVE-2018-16471
suse medium — https://www.suse.com/security/cve/CVE-2018-16471/
ubuntu medium CVE-2018-16471 medium priority: Ubuntu including 1 source packages (ruby-rack), 12 status rows across 12 suites (bionic, cosmic, disco, eoan, focal, groovy, hirsute, impish, jammy, trusty, upstream, xenial): not-affected 7, released 4, ignored 1. https://ubuntu.com/security/CVE-2018-16471

Affected software / configurations for CVE-2018-16471

Vendor Product Version Raw CPE
rack_project rack >= 1.6.0, < 1.6.11 cpe:2.3:a:rack_project:rack:*:*:*:*:*:*:*:*
rack_project rack >= 2.0.0, < 2.0.6 cpe:2.3:a:rack_project:rack:*:*:*:*:*:*:*:*
debian debian_linux 8.0 cpe:2.3:o:debian:debian_linux:8.0:*:*:*:*:*:*:*

References for CVE-2018-16471

cvelogic Threat Intelligence