CVE-2026-47138: Parse Server Denial of Service Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-38m6-82c8-4xfm",
  "modified" : "2026-06-12T21:59:40Z",
  "published" : "2026-05-23T00:11:25Z",
  "aliases" : [ "CVE-2026-47138" ],
  "summary" : "Parse Server: Pre-authentication denial of service via client version header regex backtracking",
  "details" : "### Impact\n\nAn unauthenticated attacker who knows a publicly-known Parse Application ID can submit a single HTTP request whose client SDK version field contains adversarial input that triggers polynomial backtracking in a request-header parser. The parsing runs before session authentication and before rate limiting on every `/parse/*` request, so the request consumes seconds to minutes of synchronous CPU on a Node.js worker before any access control evaluates it. A small number of concurrent requests can saturate a worker; a single large request via the body-field variant can pin a worker for minutes. Production deployments running the default configuration are affected.\n\n### Patches\n\nThe client SDK version capture and parsing have been removed entirely. The Parse JS SDK compatibility table defines a strict version-pinned contract between Parse Server and the Parse JS SDK; server-side adaptation to client SDK version is an obsolete pattern that contradicts that contract. The vulnerable parser, the `clientSDK` parameter that threaded its output through routers, and the legacy code path it gated are all removed. The `X-Parse-Client-Version` header and `_ClientVersion` JSON body field are now silently ignored on every request; supported Parse SDKs are unaffected.\n\n### Workarounds\n\nDeploy a reverse proxy or WAF in front of Parse Server that strips or strictly size-limits the `X-Parse-Client-Version` header AND the `_ClientVersion` field in JSON request bodies on every `/parse/*` route before forwarding to the server. A header-size cap alone is insufficient: the body-field variant requires inspection of JSON content. Upgrading to the patched version is the recommended remediation.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/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.1"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "npm",
      "name" : "parse-server"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "8.6.77"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/parse-community/parse-server/security/advisories/GHSA-38m6-82c8-4xfm"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-47138"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/parse-community/parse-server/pull/10463"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/parse-community/parse-server/pull/10464"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/parse-community/parse-server"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-1333" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-05-23T00:11:25Z",
    "nvd_published_at" : "2026-06-12T19:16:28Z"
  }
}