{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "MISP",
          "repo": "https://github.com/MISP/MISP",
          "vendor": "MISP",
          "versions": [
            {
              "lessThanOrEqual": "2.5.45",
              "status": "affected",
              "version": "0",
              "versionType": "semver"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "finder",
          "value": "Scottish Government - National Cyber Team"
        },
        {
          "lang": "en",
          "type": "remediation developer",
          "value": "iglocska"
        },
        {
          "lang": "en",
          "type": "remediation developer",
          "value": "Claude Opus 5 (1M context)"
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "supportingMedia": [
            {
              "base64": false,
              "type": "text/html",
              "value": "\u003cp\u003eAffected versions of MISP validate the user-configurable homepage by checking only whether the supplied path begins with \u003ccode\u003e/\u003c/code\u003e. That check is insufficient because protocol-relative URLs such as \u003ccode\u003e//attacker.example\u003c/code\u003e also begin with \u003ccode\u003e/\u003c/code\u003e but resolve to an external origin in browsers.\u003c/p\u003e\n\u003cp\u003eThe vulnerable homepage value can be stored as a user setting and later used by the post-login routing logic. The commit explicitly identifies \u003ccode\u003e//attacker.example\u003c/code\u003e as a payload that passed validation and was emitted to the \u003ccode\u003eLocation\u003c/code\u003e header after login.\u003c/p\u003e\u003cp\u003eThe fix introduces a shared \u003ccode\u003eInternalRedirectValidator\u003c/code\u003e that rejects URLs containing a host, scheme, userinfo, unsafe leading \u003ccode\u003e//\u003c/code\u003e or \u003ccode\u003e/\\\u003c/code\u003e, malformed URLs, and control characters. It also revalidates homepage settings on read so legacy or internally written unsafe values cannot bypass the new storage-time validation.\u003c/p\u003eVersion affected: \u22642.5.45"
            }
          ],
          "value": "Affected versions of MISP validate the user-configurable homepage by checking only whether the supplied path begins with /. That check is insufficient because protocol-relative URLs such as //attacker.example also begin with / but resolve to an external origin in browsers.\n\n\nThe vulnerable homepage value can be stored as a user setting and later used by the post-login routing logic. The commit explicitly identifies //attacker.example as a payload that passed validation and was emitted to the Location header after login.\n\nThe fix introduces a shared InternalRedirectValidator that rejects URLs containing a host, scheme, userinfo, unsafe leading // or /\\, malformed URLs, and control characters. It also revalidates homepage settings on read so legacy or internally written unsafe values cannot bypass the new storage-time validation.\n\nVersion affected: \u22642.5.45"
        }
      ],
      "impacts": [
        {
          "capecId": "CAPEC-178",
          "descriptions": [
            {
              "lang": "en",
              "value": "CAPEC-178 Cross-Site Flashing"
            }
          ]
        }
      ],
      "metrics": [
        {
          "cvssV4_0": {
            "Automatable": "NOT_DEFINED",
            "Recovery": "NOT_DEFINED",
            "Safety": "NOT_DEFINED",
            "attackComplexity": "LOW",
            "attackRequirements": "NONE",
            "attackVector": "NETWORK",
            "baseScore": 5.1,
            "baseSeverity": "MEDIUM",
            "privilegesRequired": "LOW",
            "providerUrgency": "NOT_DEFINED",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "LOW",
            "userInteraction": "PASSIVE",
            "valueDensity": "NOT_DEFINED",
            "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N",
            "version": "4.0",
            "vulnAvailabilityImpact": "NONE",
            "vulnConfidentialityImpact": "NONE",
            "vulnIntegrityImpact": "NONE",
            "vulnerabilityResponseEffort": "NOT_DEFINED"
          },
          "format": "CVSS",
          "scenarios": [
            {
              "lang": "en",
              "value": "GENERAL"
            }
          ]
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-601",
              "description": "CWE-601 URL Redirection to Untrusted Site (\u0027Open Redirect\u0027)",
              "lang": "en",
              "type": "CWE"
            }
          ]
        },
        {
          "descriptions": [
            {
              "cweId": "CWE-20",
              "description": "CWE-20 Improper Input Validation",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "orgId": "00000000-0000-4000-9000-000000000000"
      },
      "references": [
        {
          "tags": [
            "patch"
          ],
          "url": "https://github.com/MISP/MISP/commit/bd454f65a"
        }
      ],
      "source": {
        "discovery": "UNKNOWN"
      },
      "title": "MISP User Homepage Validation Allows Authenticated Open Redirect via Protocol-Relative URL",
      "x_generator": {
        "engine": "Vulnogram 0.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "00000000-0000-4000-9000-000000000000",
    "cveId": "CVE-2026-86351",
    "datePublished": "2026-09-07T09:59:27.107009Z",
    "dateReserved": "2026-09-07T09:59:32.940Z",
    "dateUpdated": "2026-09-07T09:59:33.009583Z",
    "requesterUserId": "00000000-0000-4000-9000-000000000000",
    "serial": 1,
    "state": "PUBLISHED",
    "vulnId": "gcve-1-2026-20152"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.1"
}