CWE-1386: Insecure Operation on Windows Junction / Mount Point
Description
The product opens a file or directory, but it does not properly prevent the name from being associated with a junction or mount point to a destination that is outside of the intended control sphere.
Depending on the intended action being performed, this could allow an attacker to cause the product to read, write, delete, or otherwise operate on unauthorized files. In Windows, NTFS5 allows for file system objects called reparse points. Applications can create a hard link from one directory to another directory, called a junction point. They can also create a mapping from a directory to a drive letter, called a mount point. If a file is used by a privileged program, but it can be replaced with a hard link to a sensitive file (e.g., AUTOEXEC.BAT), an attacker could escalate privileges. When the process opens the file, the attacker can assume the privileges of that process, tricking the privileged process to read, modify, or delete the sensitive file, preventing the program from accurately processing data. Note that one can also point to registries and semaphores.
- Abstraction
- BaseA weakness specific enough to point to detection and prevention methods.
- Likelihood of exploit
- Not rated by MITRE
- Status
- Incomplete
Common consequences
- Confidentiality
Read Files or Directories
Read arbitrary files by replacing a user-controlled folder with a mount point and additional hard links.
- Integrity
Modify Files or Directories
Modify an arbitrary file by replacing the rollback files in installer directories, as they can have the installer execute those rollbacks.
- Availability
Modify Files or Directories
Even if there is no control of contents, an arbitrary file delete or overwrite (when running as SYSTEM or admin) can be used for a permanent system denial-of-service, e.g. by deleting a startup configuration file that prevents the service from starting.
Potential mitigations
- Architecture and DesignSeparation of Privilege
When designing software that will have different rights than the executer, the software should check that files that it is interacting with are not improper hard links or mount points. One way to do this in Windows is to use the functionality embedded in the following command: dir /al /s /b or, in PowerShell, use LinkType as a filter. In addition, some software uses authentication via signing to ensure that the file is the correct one to use. Make checks atomic with the file action, otherwise a TOCTOU weakness (CWE-367) can be introduced.
Related weaknesses
Parent weaknesses
CAPEC attack patterns that exploit it
CWE 4.20 links no CAPEC attack pattern to this weakness.