Weakness · Medium
CWE-1386: Insecure Operation on Windows Junction / Mount Point
What it is
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.
- Severity (our rating)
- Medium
- Likelihood of exploit
- Not rated by MITRE
- Introduced during
- Implementation
- Exploited in the wild
- 3 known exploited CVEs
In more detail
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 excalate 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.
What an attacker can do
- Read Files or Directories (Confidentiality)
- Modify Files or Directories (Integrity, Availability)
How to prevent it
Architecture and Design
- 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.
Exploited in the wild: 3 CVEs
Vulnerabilities caused by CWE-1386 that attackers have used, from CISA's Known Exploited Vulnerabilities catalog, newest first.
- CVE-2022-21919Microsoft Windows User Profile Service Privilege Escalation Vulnerability · added April 25, 2022
- CVE-2022-21999 ransomwareMicrosoft Windows Print Spooler Privilege Escalation Vulnerability · added March 25, 2022
- CVE-2021-41379 ransomwareMicrosoft Windows Installer Privilege Escalation Vulnerability · added March 3, 2022
H2 Security
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Start freeSource: MITRE Common Weakness Enumeration, CWE version 4.19.1. CWE is a trademark of The MITRE Corporation.