Link following in Western Digital My Cloud devices

1) Link following

EUVDB-ID: #VU51481

Risk: High

CVSSv3.1: 8.8 [CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:P/RL:O/RC:C]

CVE-ID: CVE-2021-3310

CWE-ID: CWE-59 - Improper Link Resolution Before File Access ('Link Following')

Exploit availability: Yes

Description

The vulnerability allows a remote attacker to execute arbitrary code on the target system.

The vulnerability exists due to the affected software mishandle Symbolic Link Following within the SMB and AFP services. A remote attacker can create a symlink to read arbitrary files and gain access to sensitive information or execute arbitrary code on the system.

Mitigation

Install updates from vendor's website.

Vulnerable software versions

My Cloud EX2 Ultra: before 5.10.122

My Cloud Mirror Gen 2: before 5.10.122

My Cloud EX4100: before 5.10.122

My Cloud PR2100: before 5.10.122

My Cloud PR4100: before 5.10.122

My Cloud DL2100: before 5.10.122

My Cloud DL4100: before 5.10.122

My Cloud EX2100: before 5.10.122

My Cloud (P/N: WDBCTLxxxxxx-10): before 5.10.122

External links

http://www.westerndigital.com/support/productsecurity/wdc-21002-my-cloud-firmware-version-5-10-122
http://www.zerodayinitiative.com/advisories/ZDI-21-277/

Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability. However, proof of concept for this vulnerability is available.