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Weakness (CWE)

CWE-1386: Insecure Operation on Windows Junction / Mount Point

Base Incomplete

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.

More detail

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.

How to prevent it (1 mitigation)

  1. 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.

Source: MITRE CWE-1386

All Critical High Medium Low Exploited only Public exploit

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