Let's Chat 0.3.0 - 0.4.8 Broken Access Control File Disclosure via GET /files route

{
  "id": "9d63fc2605d1569182a45ce0c7c62f218c1df1702aae167c5f25ef363527689c",
  "url": "https://osv.dev/vulnerability/CVE-2026-66750",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Let's Chat 0.3.0 - 0.4.8 Broken Access Control File Disclosure via GET /files route",
    "summary": "Let's Chat 0.3.0 through 0.4.8 contains a broken access control vulnerability that allows authenticated attackers to download file attachments from private and password-protected rooms they are not a member of by exploiting missing room membership checks in the file retrieval route. Attackers can enumerate adjacent MongoDB ObjectIds derived from a known file ID to recover files uploaded by other users, as the GET /files/:id/:name route in app/controllers/files.js only enforces login authentication without consulting room membership or the Room.canJoin check.",
    "evidence": "osv:CVE-2026-66750",
    "products": [],
    "severity": "medium",
    "structured": {
      "id": "CVE-2026-66750",
      "aliases": [
        "CVE-2026-66750"
      ],
      "metrics": [
        {
          "type": "CVSS_V4",
          "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/sdelements/lets-chat",
              "type": "GIT",
              "events": [
                {
                  "introduced": "55e8833974c83559ed2cbc12bc15febeb2466254"
                },
                {
                  "last_affected": "617207ff3c0c0bf8e3c7a915bd9ec03f1dd8390c"
                },
                {
                  "introduced": "4795dc006f2c820bb11f3e9b5256017830f274db"
                },
                {
                  "last_affected": "a5e8b2d5977fedc167e1efb03a4f80121da4842e"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "55e8833974c83559ed2cbc12bc15febeb2466254"
                      },
                      {
                        "last_affected": "617207ff3c0c0bf8e3c7a915bd9ec03f1dd8390c"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StandardRange"
                  },
                  {
                    "range": [
                      {
                        "introduced": "0.3.0"
                      },
                      {
                        "last_affected": "0.4.8"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StandardRange"
                  }
                ]
              }
            }
          ],
          "versions": [
            "0.4.8",
            "0.4.7",
            "0.4.6",
            "0.4.5",
            "0.4.4",
            "0.4.3",
            "0.4.2",
            "0.4.1",
            "0.4.0",
            "0.3.6",
            "0.3.5",
            "0.3.4",
            "0.3.3",
            "0.3.2",
            "0.3.1",
            "0.3.0"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-66750.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:27.633079369Z",
      "provider": "osv",
      "references": [
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/66xxx/CVE-2026-66750.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-66750",
        "https://www.vulncheck.com/advisories/let-s-chat-broken-access-control-file-disclosure-via-get-files-route",
        "https://github.com/sdelements/lets-chat",
        "https://github.com/theopaid/Insufficient-Access-Controls-Allow-for-Unauthorized-File-Downloads-Let-s-Chat-"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-862"
        ],
        "cna_assigner": "VulnCheck",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/66xxx/CVE-2026-66750.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-66750",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 494410,
  "published_at": "2026-07-28T15:33:04.344+00:00"
}