CVE-2026-53726: parse-server Relation `$relatedTo` Query Bypasses `protectedFields` Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-wmwx-jr2p-4j4r",
  "modified" : "2026-06-19T19:35:19Z",
  "published" : "2026-06-19T19:35:19Z",
  "aliases" : [ "CVE-2026-53726" ],
  "summary" : "parse-server: Relation `$relatedTo` query bypasses `protectedFields` and owning-object ACL",
  "details" : "### Impact\n\nA relation query using the `$relatedTo` operator could read the membership of a `Relation` field even when that field was hidden from the requesting client by `protectedFields`, and even when the object owning the relation was not readable by the client under its ACL or class-level permissions. The request requires only the public API credentials that Parse clients normally carry — no user session, master key, or Cloud Code is needed.\n\nAs a result, an unauthenticated client who knows or obtains the owning object's `objectId` could enumerate the objects linked through a protected relation, or combine the operator with an `objectId` constraint to use it as a membership oracle — confirming whether a specific object is linked to a private parent. This affects applications that rely on `protectedFields` or object ACLs to keep `Relation` membership confidential, such as private group memberships, block lists, or account-to-resource associations.\n\n### Patches\n\nThe relation query path now authorizes `$relatedTo` against the owning object before reading the relation join table, using the caller's authentication context. The relation key is checked against the owning class's `protectedFields` (the query is rejected if the key is protected), and the owning object must be readable by the caller under its class-level permissions, ACL, and pointer permissions; otherwise the relation returns no results. Master and maintenance requests are unaffected. The check is applied consistently whether `$relatedTo` is used at the top level or nested within `$or`, `$and`, or `$nor`.\n\n### Workarounds\n\nThere is no complete workaround without upgrading. As mitigation, applications can avoid exposing sensitive membership through `Relation` fields to untrusted clients, or enforce access on the queried class in a `beforeFind` trigger.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "parse-server"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "9.0.0"
      }, {
        "fixed" : "9.9.1-alpha.6"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "npm",
      "name" : "parse-server"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "8.6.80"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/parse-community/parse-server/security/advisories/GHSA-wmwx-jr2p-4j4r"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-53726"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/parse-community/parse-server/pull/10493"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/parse-community/parse-server/pull/10494"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/parse-community/parse-server"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-639" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-06-19T19:35:19Z",
    "nvd_published_at" : "2026-06-12T19:16:30Z"
  }
}