CVE-2026-125109 (GCVE-0-2026-125109)

Vulnerability from cvelistv5 – Published: 2026-11-09 21:57 – Updated: 2026-11-09 21:57
VLAI
Title
Rack: Rack::Request#host_with_port (and #base_url / #url) return the raw invalid Host header — incomplete fix of CVE-2026-34835
Summary
Rack is a modular Ruby web server interface. From 3.0 until 3.1.23 and 3.2.8, Rack::Request#host_with_port, #base_url, and #url can return an attacker-controlled invalid authority from Host, X-Forwarded-Host, or Forwarded: host= verbatim. Applications without an independent host allowlist that use these methods for absolute URLs, redirects, or origin-dependent checks can emit attacker-chosen delimiters, enabling redirect manipulation, string-based allowlist bypass, or unescaped markup reflection. Rails overrides these methods and is not expected to be affected. This issue is fixed in versions 3.1.23 and 3.2.8.
Severity
4.8 (Medium)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N
CWE
  • CWE-1286 - Improper Validation of Syntactic Correctness of Input
Assigner
GitHub_M CNA
References
Impacted products
Vendor Product Version
rack rack Affected: >= 3.0, < 3.1.23
Affected: >= 3.2, < 3.2.8
Create a notification for this product.
Show details on NVD website
To clipboard 

{
  "containers": {
    "cna": {
      "affected": [
        {
          "product": "rack",
          "vendor": "rack",
          "versions": [
            {
              "status": "affected",
              "version": "\u003e= 3.0, \u003c 3.1.23"
            },
            {
              "status": "affected",
              "version": "\u003e= 3.2, \u003c 3.2.8"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "Rack is a modular Ruby web server interface. From 3.0 until 3.1.23 and 3.2.8, Rack::Request#host_with_port, #base_url, and #url can return an attacker-controlled invalid authority from Host, X-Forwarded-Host, or Forwarded: host= verbatim. Applications without an independent host allowlist that use these methods for absolute URLs, redirects, or origin-dependent checks can emit attacker-chosen delimiters, enabling redirect manipulation, string-based allowlist bypass, or unescaped markup reflection. Rails overrides these methods and is not expected to be affected. This issue is fixed in versions 3.1.23 and 3.2.8."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "HIGH",
            "attackVector": "NETWORK",
            "availabilityImpact": "NONE",
            "baseScore": 4.8,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "LOW",
            "integrityImpact": "LOW",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N",
            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-1286",
              "description": "CWE-1286: Improper Validation of Syntactic Correctness of Input",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-11-09T21:57:46.924Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/rack/rack/security/advisories/GHSA-2j8w-xcrc-x985",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/rack/rack/security/advisories/GHSA-2j8w-xcrc-x985"
        },
        {
          "name": "https://github.com/rack/rack/commit/4380381a56dc52556a436d6d794c8e18dc8b0565",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/rack/rack/commit/4380381a56dc52556a436d6d794c8e18dc8b0565"
        },
        {
          "name": "https://github.com/rack/rack/commit/49386f460286b7346c7003b69a839de782cc8a39",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/rack/rack/commit/49386f460286b7346c7003b69a839de782cc8a39"
        },
        {
          "name": "https://github.com/rack/rack/releases/tag/v3.1.23",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/rack/rack/releases/tag/v3.1.23"
        },
        {
          "name": "https://github.com/rack/rack/releases/tag/v3.2.8",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/rack/rack/releases/tag/v3.2.8"
        }
      ],
      "source": {
        "advisory": "GHSA-2j8w-xcrc-x985",
        "discovery": "UNKNOWN"
      },
      "title": "Rack: Rack::Request#host_with_port (and #base_url / #url) return the raw invalid Host header \u2014 incomplete fix of CVE-2026-34835"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-125109",
    "datePublished": "2026-11-09T21:57:46.924Z",
    "dateReserved": "2026-11-09T17:45:35.935Z",
    "dateUpdated": "2026-11-09T21:57:46.924Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.




Drag nodes to arrange them. Double-click a related vulnerability to open it, or a source to visit its link. The Physics button on the left tunes the layout and the simulation; the legend at the bottom left hides or shows nodes by kind and by sighting type.

Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
Vulnerability timeline

Sightings and recorded dates, grouped by day · UTC

JSON

Loading timeline…




    Related by attack behaviour

    Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.