CVE-2026-34785 | Rack: Local file inclusion in `Rack::Static` via URL Prefix Matching

Rack is a modular Ruby web server interface. Prior to versions 2.2.23, 3.1.21, and 3.2.6, Rack::Static determines whether a request should be served as a static file using a simple string prefix check. When configured with URL prefixes such as "/css", it matches any request path that begins with that string, including unrelated paths such as "/css-config.env" or "/css-backup.sql". As a result, files under the static root whose names merely share the configured prefix may be served unintentionally, leading to information disclosure. This issue has been patched in versions 2.2.23, 3.1.21, and 3.2.6.

Published: 2026-04-02 Last update: 2026-04-16 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-34785 is rated Low Risk (33.1/100): CVSS High severity, with low exploitation likelihood (EPSS 0.03%). 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-2026-34785

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 2026-04-03 — 0.03% —

Full EPSS history (1 record total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-34785

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:H/I:N/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: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:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:N)
Service keeps running; no real outage angle.
 3.9 3.6 [email protected]

Weakness enumeration for CVE-2026-34785

GitHub Security Advisory for CVE-2026-34785

GHSA-h2jq-g4cq-5ppq · Severity: high · Ecosystem: rubygems — Rack::Static prefix matching can expose unintended files under the static root

OS Trackers for CVE-2026-34785

vendor priority summary link
debian not yet assigned CVE-2026-34785 not yet assigned priority: Debian including 1 source packages (ruby-rack), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): open 3, resolved 2. https://security-tracker.debian.org/tracker/CVE-2026-34785
redhat high — https://access.redhat.com/security/cve/CVE-2026-34785
suse high CVE-2026-34785 severity important: SUSE including 2 source package names (hawk2, ruby4.0-rubygem-rack-2.2-2.2.23-1.1), 7 product×package rows across 7 product lines (SUSE Linux Enterprise High Availability Extension 12 SP5, SUSE Linux Enterprise High Availability Extension 15 SP4, … (7 product lines)): Known Not Affected 6, Fixed 1. https://www.suse.com/security/cve/CVE-2026-34785/
ubuntu medium CVE-2026-34785 medium priority: Ubuntu including 1 source packages (ruby-rack), 9 status rows across 9 suites (bionic, focal, jammy, noble, questing, resolute, trusty, upstream, xenial): released 7, needed 1, not-affected 1. https://ubuntu.com/security/CVE-2026-34785

Affected software / configurations for CVE-2026-34785

Vendor Product Version Raw CPE
rack rack < 2.2.23 cpe:2.3:a:rack:rack:*:*:*:*:*:ruby:*:*
rack rack >= 3.0.0, < 3.1.21 cpe:2.3:a:rack:rack:*:*:*:*:*:ruby:*:*
rack rack >= 3.2.0, < 3.2.6 cpe:2.3:a:rack:rack:*:*:*:*:*:ruby:*:*

References for CVE-2026-34785

cvelogic Threat Intelligence