Détail du CWE-1386

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 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.

Modes d'introduction

Implementation : The developer might not consider that when a program in Windows operates with different permissions than the executing user, the use of links, mount points, and junctions might cause the program to access files or directories that are outside of the intended storage location.

Plateformes applicables

Langue

Class: Not Language-Specific (Undetermined)

Systèmes d’exploitation

Class: Windows (Undetermined)

Conséquences courantes

Exemples observés

Mesures d’atténuation potentielles

Phases : 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.

Notes de cartographie des vulnérabilités

Justification : This CWE entry is at the Base level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.
Commentaire : Carefully read both the name and description to ensure that this mapping is an appropriate fit. Do not try to 'force' a mapping to a lower-level Base/Variant simply to comply with this preferred level of abstraction.

NotesNotes

Symbolic links, hard links, junctions, and mount points can be confusing terminology, as there are differences in how they operate between UNIX-based systems and Windows, and there are interactions between them.
This entry is still under development and will continue to see updates and content improvements.

Références

REF-1262

Follow the Link: Exploiting Symbolic Links with Ease
Eran Shimony.
https://www.cyberark.com/resources/threat-research-blog/follow-the-link-exploiting-symbolic-links-with-ease

REF-1264

Windows 10^H^H Symbolic Link Mitigations
James Forshaw.
https://googleprojectzero.blogspot.com/2015/08/windows-10hh-symbolic-link-mitigations.html

REF-1265

Symbolic testing tools
https://github.com/googleprojectzero/symboliclink-testing-tools

REF-1266

Understanding and Exploiting Symbolic links in Windows - Symlink Attack EOP
Shubham Dubey.
https://nixhacker.com/understanding-and-exploiting-symbolic-link-in-windows/

REF-1267

Abusing Arbitrary File Deletes to Escalate Privilege and Other Great Tricks
Simon Zuckerbraun.
https://www.zerodayinitiative.com/blog/2022/3/16/abusing-arbitrary-file-deletes-to-escalate-privilege-and-other-great-tricks

REF-1271

Abusing privileged file operations
Clément Lavoillotte.
https://troopers.de/troopers19/agenda/7af9hw/

Soumission

Modifications