Umbraco CMS before 17.7.2 and 18.2.2 Account Takeover via Host Header Poisoning

{
  "id": "d2bcc0fa11cd4feaae0336c7036a66e524acf7526f8f02f91c057a9bb33c2ace",
  "url": "https://www.cve.org/CVERecord?id=CVE-2026-117553",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Umbraco CMS before 17.7.2 and 18.2.2 Account Takeover via Host Header Poisoning",
    "summary": "Umbraco CMS before 17.7.2 and 18.2.2 contains an authentication bypass vulnerability that allows unauthenticated attackers to register attacker-controlled OAuth redirect URIs by poisoning the Host header. Attackers send signed-in users authorization links using response_mode=form_post to capture codes, then redeem them via HTTP Basic client credentials to hijack back-office sessions and execute code through Razor templates.",
    "evidence": "cve:CVE-2026-117553",
    "products": [
      {
        "name": {
          "value": "Umbraco-CMS",
          "evidence": "/containers/cna/affected/0/product"
        },
        "prerequisites": [],
        "fixed_versions": [],
        "affected_versions": []
      }
    ],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-117553",
      "aliases": [
        "CVE-2026-117553"
      ],
      "metrics": [
        {
          "format": "CVSS",
          "cvssV4_0": {
            "version": "4.0",
            "baseScore": 7.7,
            "attackVector": "NETWORK",
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N",
            "userInteraction": "PASSIVE",
            "attackComplexity": "LOW",
            "attackRequirements": "PRESENT",
            "privilegesRequired": "NONE",
            "subIntegrityImpact": "NONE",
            "vulnIntegrityImpact": "HIGH",
            "subAvailabilityImpact": "NONE",
            "vulnAvailabilityImpact": "HIGH",
            "subConfidentialityImpact": "NONE",
            "vulnConfidentialityImpact": "HIGH"
          }
        },
        {
          "format": "CVSS",
          "cvssV3_1": {
            "scope": "UNCHANGED",
            "version": "3.1",
            "baseScore": 7.5,
            "attackVector": "NETWORK",
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H",
            "integrityImpact": "HIGH",
            "userInteraction": "REQUIRED",
            "attackComplexity": "HIGH",
            "availabilityImpact": "HIGH",
            "privilegesRequired": "NONE",
            "confidentialityImpact": "HIGH"
          }
        }
      ],
      "affected": [
        {
          "vendor": "umbraco",
          "product": "Umbraco-CMS",
          "versions": [
            {
              "status": "affected",
              "version": "0",
              "lessThan": "17.7.2",
              "versionType": "semver"
            },
            {
              "status": "affected",
              "version": "18.0.0",
              "lessThan": "18.2.2",
              "versionType": "semver"
            }
          ],
          "packageURL": "pkg:nuget/Umbraco.Cms",
          "defaultStatus": "unaffected"
        }
      ],
      "modified": "2026-10-27T13:07:49.671Z",
      "provider": "cve",
      "references": [
        "https://github.com/umbraco/Umbraco-CMS/commit/490b9b27dcbb8fb3fe868a36203590968b0569d6",
        "https://github.com/umbraco/Umbraco-CMS",
        "https://github.com/umbraco/Umbraco-CMS/security/advisories/GHSA-rpv9-qp4c-g469",
        "https://github.com/umbraco/Umbraco-CMS/blob/release-18.2.1/src/Umbraco.Cms.Api.Management/Middleware/BackOfficeAuthorizationInitializationMiddleware.cs#L74-L112",
        "https://www.vulncheck.com/advisories/umbraco-cms-before-17.7.2-and-18.2.2-account-takeover-via-host-header-poisoning"
      ],
      "provider_metadata": {
        "cna": {
          "orgId": "83251b91-4cc7-4094-a5c7-464a1b83ea10",
          "shortName": "VulnCheck",
          "dateUpdated": "2026-10-27T13:07:49.671Z"
        }
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-117553",
        "evidence": "/cveMetadata/cveId"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/containers/cna/metrics"
  },
  "source_id": "core-cve",
  "document_id": 392681,
  "published_at": "2026-10-27T13:07:49.671+00:00"
}