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Fencer Vulns
high 7.5

CVE-2026-34785 json

Rack: Local file inclusion in `Rack::Static` via URL Prefix Matching

published 2026-04-02 7 mo ago modified 2026-09-10 1 mo ago also EUVD-2026-18382 , GHSA-h2jq-g4cq-5ppq

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 33%
public exploits
0
none known

Summary

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.

Patch / fix

  • rubygems rack 2.2.23, 3.1.21, 3.2.6
  • rack rack 2.2.23, 3.1.21, 3.2.6
  • rack_project rack 2.2.23, 3.1.21, 3.2.6
  • ruby-rack Debian 12 2.2.22-0+deb12u2
  • ruby-rack Debian 13 3.1.20-0+deb13u2
  • ruby-rack Debian 14 3.2.6-2

debian advisories DEBIAN-CVE-2026-34785

  • ruby-rack Ubuntu 24.04 LTS 2.2.7-1ubuntu0.7
  • ruby-rack Ubuntu 25.10 3.1.16-0.1ubuntu0.3
  • ruby-rack Ubuntu 26.04 LTS 3.2.4-1ubuntu1.1
  • ruby-rack Ubuntu Pro 14.04 LTS 1.5.2-3+deb8u3ubuntu1~esm11
  • ruby-rack Ubuntu Pro 16.04 LTS 1.6.4-3ubuntu0.2+esm10
  • ruby-rack Ubuntu Pro 18.04 LTS 1.6.4-4ubuntu0.2+esm10
  • ruby-rack Ubuntu Pro 22.04 LTS 2.1.4-5ubuntu1.2+esm3

ubuntu advisories UBUNTU-CVE-2026-34785

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • rmt-server SLES for SAP applications 16.0, SLES 16.0 3.1.0-160000.1.1
  • rmt-server SLES for SAP 15 SP6, SLES for SAP 15 SP5, SLES 15 SP6-LTSS +5 more 2.27-150500.3.47.1

suse advisories SUSE-SU-2026:23321-1SUSE-SU-2026:2487-1

  • rmt-server openSUSE Leap 16.0 3.1.0-160000.1.1
  • rubygem-rack-2.2 openSUSE Tumbleweed 2.2.23-1.1

opensuse advisories openSUSE-SU-2026:21640-1openSUSE-SU-2026:10508-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-34785 updated cvss 7.5

github.com/rack/rack: Rack: Information disclosure via incorrect static file serving prefix check

  • Red Hat Satellite 6 rubygem-rack, rubygem-rack-test
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
7 mo ago

Exploit prediction

0.39% chance of exploitation in the next 30 days, higher than 33% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
CISA ADP 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
GitHub 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Affected packages

ecosystem package affected fixed in
rubygems rack
<2.2.23
>=3.0.0.beta1, <3.1.21
>=3.2.0, <3.2.6
2.2.23
3.1.21
3.2.6

Affected products

  • rack rack
  • Red Hat Red Hat Satellite 6

Classification

Weakness
  • CWE-187 Partial String Comparison
  • CWE-200 Exposure of Sensitive Information to an Unauthorized Actor
  • CWE-552 Files or Directories Accessible to External Parties

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.