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CVE-2026-125109VulnerabilityPublished Updated

Ruby rack: From 3.0 until 3.1.23 and 3.2.8, Rack::Request#host_with_port, #base_url, and #url can return an

Affects ruby-rackSource GCVE Database

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Authoritative record:CVE-2026-125109· Medium 4.8

Not known to be exploited · CVSS 4.8 Medium · fixed in 3.1.23 : update ruby-rack when convenient.

Data as of 13 Nov 2026, 22:38 UTC

CVSS 3.1 base score
4.8Medium
How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none
CVSS scores by source
CNA (GitHub_M)CVSS 3.14.8
Patch
Available – fixed in 3.1.23
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 9 Nov 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 13 Nov 2026.

What to do

Affected software

ProductAffectedFixed in
Ubuntu 26.10ruby-rackpkg:deb/ubuntu/ruby-rack?arch=source&distro=stonkingOther threatsAffected
  • =3.2.4-1ubuntu1
  • =3.2.6-3
Fixed in–
Ubuntu 26.04 LTSruby-rackpkg:deb/ubuntu/ruby-rack?arch=source&distro=resoluteOther threatsAffected
  • 3.1.16-0.1 – 3.2.4-1ubuntu1.1
5 affected builds
Fixed in–
Ubuntu 24.04 LTSruby-rackpkg:deb/ubuntu/ruby-rack?arch=source&distro=nobleOther threatsAffected
  • 2.2.4-3 – 2.2.7-1ubuntu0.7
9 affected builds
Fixed in–
Ubuntu Pro 22.04 LTSruby-rackpkg:deb/ubuntu/ruby-rack?arch=source&distro=esm-apps/jammyOther threatsAffected
  • 2.1.4-3 – 2.1.4-5ubuntu1+esm5
15 affected builds
Fixed in–
Ubuntu Pro 20.04 LTSruby-rackpkg:deb/ubuntu/ruby-rack?arch=source&distro=esm-apps/focalOther threatsAffected
  • 2.0.6-3 – 2.0.7-2ubuntu0.1+esm10
13 affected builds
Fixed in–
Ubuntu Pro 18.04 LTSruby-rackpkg:deb/ubuntu/ruby-rack?arch=source&distro=esm-apps/bionicOther threatsAffected
  • 1.6.4-4 – 1.6.4-4ubuntu0.2+esm10
12 affected builds
Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Upgrade Ruby Rack to version 3.1.23 or later, or 3.2.8 or later, where this vulnerability is fixed. Applications should also implement independent host allowlisting or validation rather than relying solely on these methods for host information. Since the vendor advisory confirms fixes in these versions, applying these updates fully mitigates the issue.

Description

A vulnerability in Ruby Rack versions from 3.0 up to but not including 3.1.23 and 3.2.8 allows certain methods to return attacker-controlled invalid host information from HTTP headers. This can lead to redirect manipulation, allowlist bypass, or unescaped markup reflection in applications that rely on these methods for absolute URLs or origin checks. Rails applications are not affected due to method overrides. The issue is fixed in Rack versions 3.1.23 and 3.2.8.

References

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