Improper access control in QNAP Hybrid Backup Sync

1) Missing Authentication for Critical Function

EUVDB-ID: #VU54553

Risk: High

CVSSv4.0: [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Amber]

CVE-ID: CVE-2021-28809

CWE-ID: CWE-306 - Missing Authentication for Critical Function

Exploit availability: No

Description

The vulnerability allows a remote attacker to compromise the affected system.

The vulnerability exists due to missing authentication in the within the RTSS server. A remote non-authenticated attacker can send a specially crafted request to port 8899/TCP and execute arbitrary code in the context of the Administrator.

Mitigation

Install updates from vendor's website.

Vulnerable software versions

HBS 3 Hybrid Backup Sync: 3.0.190923 - 3.0.210412

CPE2.3

• cpe:2.3:a:qnap_systems:hbs_3_hybrid_backup_sync:3.0.190923:*:*:*:*:*:*:*
• cpe:2.3:a:qnap_systems:hbs_3_hybrid_backup_sync:3.0.191016:*:*:*:*:*:*:*
• cpe:2.3:a:qnap_systems:hbs_3_hybrid_backup_sync:3.0.191108:*:*:*:*:*:*:*

External links

http://www.qnap.com/en/security-advisory/qsa-21-19
http://www.zerodayinitiative.com/advisories/ZDI-21-783/

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.