CVE-2025-57711: Qnap Qsync Central DoS Vulnerability

CVE-2025-57711 Overview

An allocation of resources without limits or throttling vulnerability (CWE-770) has been reported affecting QNAP Qsync Central. This resource exhaustion vulnerability allows a remote attacker who has gained administrator account access to exploit the flaw and prevent other systems, applications, or processes from accessing the same type of resource, effectively causing a denial of service condition.

Critical Impact

Authenticated attackers with administrator privileges can exhaust system resources, causing denial of service and preventing legitimate access to Qsync Central synchronization services.

Affected Products

• QNAP Qsync Central versions prior to 5.0.0.4

Discovery Timeline

• 2026-01-20 - QNAP releases security patch in Qsync Central 5.0.0.4
• 2026-02-11 - CVE CVE-2025-57711 published to NVD
• 2026-02-12 - Last updated in NVD database

Technical Details for CVE-2025-57711

Vulnerability Analysis

This vulnerability stems from CWE-770: Allocation of Resources Without Limits or Throttling. The affected Qsync Central application fails to properly limit resource allocation, allowing an authenticated administrator to consume excessive resources. While the vulnerability requires high privileges (administrator access) to exploit, it can significantly impact both the vulnerable system and downstream connected systems that depend on the synchronization service.

The attack requires network access and administrator-level authentication, but once those conditions are met, an attacker can systematically exhaust resources to disrupt service availability for legitimate users and connected applications.

Root Cause

The root cause lies in insufficient resource allocation controls within Qsync Central. The application does not implement proper throttling mechanisms or resource limits for certain operations, allowing privileged users to consume resources without bounds. This design flaw enables resource exhaustion attacks that can affect both the local system and other connected systems relying on the synchronization service.

Attack Vector

The vulnerability is exploited over the network by an attacker who has already compromised or obtained administrator credentials for the Qsync Central application. The attack flow typically involves:

1. Attacker gains access to an administrator account (through credential theft, phishing, or other means)
2. Attacker authenticates to the Qsync Central management interface
3. Attacker initiates operations that trigger uncontrolled resource allocation
4. System resources become exhausted, preventing other systems and processes from functioning properly

The vulnerability mechanism involves resource allocation operations that lack proper limits or throttling controls. When exploited, the application continues to allocate resources until system capacity is exhausted, affecting service availability for all dependent processes and connected clients.

Detection Methods for CVE-2025-57711

Indicators of Compromise

• Unusual resource consumption patterns on QNAP NAS devices running Qsync Central
• Sudden spikes in memory or CPU utilization without corresponding legitimate activity
• Service unavailability or degraded performance of Qsync synchronization services
• Failed connection attempts from legitimate clients due to resource exhaustion

Detection Strategies

• Monitor system resource utilization on devices running Qsync Central for abnormal patterns
• Implement alerting for administrator login events, especially from unexpected IP addresses
• Track resource allocation metrics and establish baselines to detect anomalies
• Review audit logs for administrator actions that precede resource exhaustion events

Monitoring Recommendations

• Enable comprehensive logging for all administrative actions in Qsync Central
• Configure SNMP or other monitoring protocols to track resource utilization trends
• Implement network monitoring to detect unusual traffic patterns to the management interface
• Set up automated alerts when resource consumption exceeds established thresholds

How to Mitigate CVE-2025-57711

Immediate Actions Required

• Update QNAP Qsync Central to version 5.0.0.4 or later immediately
• Audit administrator accounts and remove any unauthorized or suspicious accounts
• Review access logs for any unusual administrator activity
• Implement strong authentication practices including multi-factor authentication where possible

Patch Information

QNAP has released a security patch addressing this vulnerability. The fix is included in Qsync Central version 5.0.0.4 released on 2026-01-20. Administrators should update to this version or later to remediate the vulnerability. For detailed information, refer to the QNAP Security Advisory QSA-26-02.

Workarounds

• Restrict network access to Qsync Central management interfaces to trusted networks only
• Implement network segmentation to limit exposure of NAS devices
• Enable and monitor audit logging to detect suspicious administrator activities
• Consider temporarily disabling Qsync Central if the service is not critical until patching is complete

# Example: Restrict access to management interface via firewall rules
# This limits access to the QNAP management interface to specific trusted networks
iptables -A INPUT -p tcp --dport 8080 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 8080 -j DROP