CVE-2024-10442: Synology Unified Controller RCE Vulnerability

CVE-2024-10442 Overview

CVE-2024-10442 is a critical off-by-one error vulnerability affecting the transmission component in Synology Replication Service and Synology Unified Controller (DSMUC). This memory corruption flaw allows remote attackers to execute arbitrary code without authentication, potentially leading to complete system compromise across affected Synology NAS devices and unified controller deployments.

Critical Impact

Remote attackers can exploit this off-by-one error to achieve arbitrary code execution on vulnerable Synology devices without requiring authentication, potentially compromising data integrity, confidentiality, and availability across the entire system.

Affected Products

• Synology Replication Service before 1.0.12-0066
• Synology Replication Service before 1.2.2-0353
• Synology Replication Service before 1.3.0-0423
• Synology Unified Controller (DSMUC) before 3.1.4-23079
• Synology DiskStation Manager versions 6.2, 7.1, and 7.2

Discovery Timeline

• 2025-03-19 - CVE-2024-10442 published to NVD
• 2026-01-16 - Last updated in NVD database

Technical Details for CVE-2024-10442

Vulnerability Analysis

This vulnerability stems from an off-by-one error (CWE-193) in the transmission component of Synology Replication Service. Off-by-one errors occur when a loop iterates one time too many or too few, or when an array index calculation results in accessing memory one position beyond or before the intended boundary. In this case, the flaw exists within the data replication transmission handling code, where improper boundary calculations allow attackers to corrupt adjacent memory structures.

The vulnerability is network-accessible, requires no user interaction or authentication, and can affect resources beyond the vulnerable component's security scope. This makes it particularly dangerous for organizations running Synology devices exposed to networks, as attackers can remotely trigger the vulnerability to execute arbitrary code with the privileges of the Replication Service process.

Root Cause

The root cause is an off-by-one error in boundary calculations within the transmission component. This type of memory corruption vulnerability typically occurs when:

• Loop conditions use incorrect comparison operators (e.g., <= instead of <)
• Buffer size calculations fail to account for null terminators or header bytes
• Array index calculations incorrectly handle edge cases

In the context of Synology Replication Service, the transmission component processes replication data where this boundary miscalculation allows writing or reading one byte beyond the intended buffer boundary, corrupting adjacent memory and enabling code execution.

Attack Vector

The attack vector is network-based, allowing remote exploitation without authentication. An attacker can target the replication service's transmission component by sending specially crafted network packets that trigger the off-by-one condition. The vulnerability's scope change characteristic indicates that successful exploitation can impact components beyond the Replication Service itself, potentially affecting the underlying DiskStation Manager operating system and other services running on the device.

The attack does not require user interaction, making it suitable for automated exploitation. Given that Synology NAS devices are often deployed in enterprise environments for backup and replication purposes, successful exploitation could provide attackers with access to sensitive corporate data and a foothold for lateral movement within the network.

Detection Methods for CVE-2024-10442

Indicators of Compromise

• Unexpected crashes or restarts of the Synology Replication Service
• Anomalous network traffic patterns to/from the replication service ports
• Unusual process spawning from Replication Service parent processes
• Unexpected modifications to system files or configurations on Synology devices

Detection Strategies

• Monitor for unusual inbound connections to Synology replication service ports from untrusted sources
• Implement network-based intrusion detection signatures for malformed replication protocol traffic
• Deploy endpoint detection solutions capable of monitoring for memory corruption exploitation attempts
• Review Synology system logs for service crashes or unexpected error patterns in the transmission component

Monitoring Recommendations

• Enable verbose logging on Synology devices to capture detailed Replication Service activity
• Configure SIEM alerts for connection attempts to replication services from external networks
• Establish baseline network behavior for replication traffic and alert on deviations
• Monitor for post-exploitation indicators such as unauthorized administrative actions or data exfiltration

How to Mitigate CVE-2024-10442

Immediate Actions Required

• Update Synology Replication Service to version 1.0.12-0066, 1.2.2-0353, or 1.3.0-0423 or later depending on your DSM version
• Update Synology Unified Controller (DSMUC) to version 3.1.4-23079 or later
• Restrict network access to replication services to trusted hosts only using firewall rules
• Audit current Synology device configurations and disable Replication Service if not actively required

Patch Information

Synology has released security patches addressing this vulnerability. Administrators should consult the Synology Security Advisory SA-24-22 for detailed patching instructions and download links. The patches are available through the standard Synology Package Center update mechanism for devices running supported DSM versions.

Workarounds

• Isolate affected Synology devices on segmented network VLANs with restricted access
• Implement strict firewall rules to block external access to replication service ports
• Disable the Replication Service package if replication functionality is not required for business operations
• Deploy a VPN requirement for all remote access to Synology management and replication interfaces
• Monitor network traffic for exploitation attempts while awaiting patch deployment

# Example: Restrict access to Synology services via iptables (on network firewall)
# Block external access to common Synology replication ports
iptables -A INPUT -p tcp --dport 5566 -s ! 10.0.0.0/8 -j DROP
iptables -A INPUT -p tcp --dport 5667 -s ! 10.0.0.0/8 -j DROP

# Allow only specific trusted hosts for replication
iptables -A INPUT -p tcp --dport 5566 -s 192.168.1.100 -j ACCEPT
iptables -A INPUT -p tcp --dport 5667 -s 192.168.1.100 -j ACCEPT