CVE-2021-28809 in QTS
Summary
by MITRE • 07/08/2021
An improper access control vulnerability has been reported to affect certain legacy versions of HBS 3. If exploited, this vulnerability allows attackers to compromise the security of the operating system.QNAP have already fixed this vulnerability in the following versions of HBS 3: QTS 4.3.6: HBS 3 v3.0.210507 and later QTS 4.3.4: HBS 3 v3.0.210506 and later QTS 4.3.3: HBS 3 v3.0.210506 and later
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Analysis
by VulDB Data Team • 07/11/2021
The vulnerability identified as CVE-2021-28809 represents a critical improper access control flaw within legacy versions of HBS 3 software, a component commonly found in QNAP network-attached storage devices. This weakness stems from inadequate authorization mechanisms that fail to properly validate user permissions and access rights, creating a pathway for unauthorized individuals to bypass security controls and gain elevated privileges within the system. The vulnerability specifically affects older iterations of the HBS 3 backup service that operates within QNAP's QTS operating system environment, where proper access controls should prevent unauthorized modification or execution of system functions.
The technical implementation of this flaw manifests through insufficient validation of user credentials and session management within the HBS 3 service architecture. Attackers exploiting this vulnerability can manipulate authentication flows or leverage existing access tokens to escalate privileges and execute arbitrary code on the underlying operating system. This improper access control vulnerability operates at the application level and can be classified under CWE-285, which specifically addresses improper authorization within software systems. The flaw essentially allows an attacker to perform actions that should be restricted to authorized administrators or system processes, potentially enabling complete system compromise and persistent access to sensitive data stored on the network-attached storage device.
From an operational standpoint, the impact of this vulnerability extends beyond simple unauthorized access to encompass full system compromise capabilities that align with ATT&CK technique T1078 for Valid Accounts and T1566 for Phishing. Organizations utilizing affected QNAP devices running legacy HBS 3 versions face significant risk of data exfiltration, system manipulation, and potential lateral movement within their network infrastructure. The vulnerability's exploitation can result in persistent backdoors, data encryption for ransomware attacks, or complete takeover of storage services that may contain critical business data, personal information, or intellectual property. Network administrators must consider that compromised QNAP devices can serve as entry points for broader network infiltration, particularly in environments where these devices are used for backup operations or as central data repositories.
Mitigation strategies for CVE-2021-28809 require immediate implementation of software updates to the patched versions of HBS 3 as specified by QNAP. Organizations should upgrade their QTS firmware to versions 4.3.6 with HBS 3 v3.0.210507 or later, 4.3.4 with HBS 3 v3.0.210506 or later, and 4.3.3 with HBS 3 v3.0.210506 or later to ensure proper access control enforcement. Additionally, system administrators should conduct comprehensive vulnerability assessments to identify any devices still operating on affected versions, implement network segmentation to limit access to storage devices, and establish monitoring protocols for unusual authentication patterns or system access attempts. Security teams should also consider disabling unnecessary backup services, implementing strict firewall rules, and maintaining detailed audit logs to detect potential exploitation attempts. The remediation process should include thorough testing of updated firmware to ensure compatibility with existing backup configurations while maintaining proper access control policies throughout the network infrastructure.