CVE-2021-27646 in DiskStation Manager
Summary
by MITRE • 03/12/2021
Use After Free vulnerability in iscsi_snapshot_comm_core in Synology DiskStation Manager (DSM) before 6.2.3-25426-3 allows remote attackers to execute arbitrary code via crafted web requests.
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Analysis
by VulDB Data Team • 01/15/2025
The vulnerability identified as CVE-2021-27646 represents a critical use-after-free flaw within the iscsi_snapshot_comm_core component of Synology DiskStation Manager DSM software. This issue affects versions prior to 6.2.3-25426-3 and creates a remote code execution vector that can be exploited through crafted web requests. The vulnerability stems from improper memory management practices where freed memory blocks are still referenced or accessed by subsequent operations, creating a scenario where attackers can manipulate the application's memory state to achieve unauthorized code execution. Such vulnerabilities are particularly dangerous in network-facing services as they can be triggered without authentication, making them attractive targets for automated exploitation campaigns.
The technical implementation of this use-after-free vulnerability occurs within the iSCSI snapshot communication core functionality of the DSM system, which handles storage virtualization operations for network-attached storage environments. When processing crafted web requests, the system fails to properly validate or manage memory references, leading to a situation where freed memory locations can be reallocated and subsequently accessed by malicious code. This memory management error creates a predictable exploitation pattern that allows remote attackers to inject and execute arbitrary code on the affected system. The flaw specifically impacts the iSCSI protocol implementation within the DSM environment, which is commonly used for enterprise storage networking and data replication scenarios.
From an operational impact perspective, this vulnerability exposes Synology DiskStation systems to significant risk including complete system compromise, data exfiltration, and potential lateral movement within network environments. The remote code execution capability means that attackers can gain full administrative control over affected storage appliances without requiring physical access or prior authentication. This creates a severe threat vector for organizations relying on Synology DSM for critical storage infrastructure, particularly in enterprise environments where these devices often serve as primary storage solutions for business-critical data. The vulnerability can be exploited by attackers from any location with network access to the affected system, making it particularly concerning for publicly accessible storage appliances.
Organizations should prioritize immediate remediation through the installation of DSM version 6.2.3-25426-3 or later, which contains the necessary memory management fixes to address the use-after-free condition. Network segmentation and access controls should be implemented to limit exposure of affected systems to untrusted networks, while monitoring systems should be configured to detect suspicious web request patterns that may indicate exploitation attempts. Security teams should also consider implementing intrusion detection systems capable of identifying the specific attack patterns associated with this vulnerability, as well as conducting comprehensive vulnerability assessments of all Synology DSM installations within their environments. The remediation process should include thorough testing of the updated firmware to ensure continued functionality of iSCSI services while eliminating the memory management vulnerability that enables remote code execution.
This vulnerability aligns with CWE-416, which specifically addresses use-after-free conditions in software implementations. The attack pattern corresponds to techniques described in the MITRE ATT&CK framework under the T1059.007 sub-technique for command and scripting interpreter, as successful exploitation would enable attackers to execute arbitrary commands on the compromised system. The vulnerability also demonstrates characteristics consistent with the ATT&CK tactic of execution, where adversaries leverage system weaknesses to run malicious code. Organizations should consider the broader implications of such vulnerabilities within their storage infrastructure security posture, as iSCSI-based storage systems often serve as critical components in enterprise data architectures and may contain sensitive organizational data requiring protection against advanced persistent threats.