An Incorrect Symlink Follow vulnerability exists in multiple Yottamaster NAS devices, including DM2 (version equal to or prior to V1.9.12), DM3 (version equal to or prior to V1.9.12), and DM200 (version equal to or prior to V1.2.23) that could be exploited by attackers to leak or tamper with the internal file system. Attackers can format a USB drive to ext4, create a symbolic link to its root directory, insert the drive into the NAS devices slot, then access the USB drives symlink directory mounted on the NAS to obtain all files within the NAS system and tamper with those files.
Weakness
The product attempts to access a file based on the filename, but it does not properly prevent that filename from identifying a link or shortcut that resolves to an unintended resource.
Affected Software
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Dm2_firmware | Yottamaster | * | 1.9.12 (including) |
Potential Mitigations
- Follow the principle of least privilege when assigning access rights to entities in a software system.
- Denying access to a file can prevent an attacker from replacing that file with a link to a sensitive file. Ensure good compartmentalization in the system to provide protected areas that can be trusted.
Related Attack Patterns
- https://cwe.mitre.org/data/definitions/132.html
- https://cwe.mitre.org/data/definitions/17.html
- https://cwe.mitre.org/data/definitions/35.html
- https://cwe.mitre.org/data/definitions/76.html