MISP User Homepage Validation Allows Authenticated Open Redirect via Protocol-Relative URL

{
  "id": "1f3086c2cf52ba1897f55718be0746e3d8b628b8e980cddc5d9a11a30514583a",
  "url": "https://osv.dev/vulnerability/CVE-2026-86351",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "MISP User Homepage Validation Allows Authenticated Open Redirect via Protocol-Relative URL",
    "summary": "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. The 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. The 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. Version affected: ≤2.5.45",
    "evidence": "osv:CVE-2026-86351",
    "products": [],
    "severity": "medium",
    "structured": {
      "id": "CVE-2026-86351",
      "aliases": [
        "CVE-2026-86351"
      ],
      "metrics": [
        {
          "type": "CVSS_V4",
          "score": "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"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/misp/misp",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "bd454f65a"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "cpe": "cpe:2.3:a:misp-project:misp:*:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "last_affected": "2.5.45"
                      }
                    ],
                    "source": "CPE_RANGE"
                  },
                  {
                    "range": [
                      {
                        "fixed": "bd454f65a"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  }
                ]
              }
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-86351.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:30.437795934Z",
      "provider": "osv",
      "references": [
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/86xxx/CVE-2026-86351.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-86351",
        "https://github.com/MISP/MISP/commit/bd454f65a",
        "https://github.com/MISP/MISP"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-20",
          "CWE-601"
        ],
        "cna_assigner": "CIRCL",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/86xxx/CVE-2026-86351.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-86351",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 497039,
  "published_at": "2026-09-07T09:59:34.85+00:00"
}