CVE-2025-14713: Synology C2 Identity Credential Exposure

CVE-2025-14713 Overview

CVE-2025-14713 is an Exposed Dangerous Method or Function vulnerability [CWE-749] in the Synology C2 Identity Edge Server package for DiskStation Manager (DSM). The flaw affects versions prior to 1.76.0-0307 and allows unauthenticated remote attackers to retrieve user credentials directly from the edge server. The vulnerability is network-accessible, requires no privileges, and needs no user interaction, making it straightforward to exploit against exposed instances.

Critical Impact

Remote attackers can extract user credentials from the Synology C2 Identity Edge Server without authentication, enabling downstream account takeover and lateral movement into identity-connected systems.

Affected Products

• Synology C2 Identity Edge Server package on DSM versions before 1.76.0-0307
• Synology DSM deployments running the C2 Identity Edge Server role
• Identity-federated environments relying on the affected edge server for authentication brokering

Discovery Timeline

• 2026-05-27 - CVE-2025-14713 published to NVD
• 2026-05-27 - Last updated in NVD database
• Reference - Synology Security Advisory SA-25-18

Technical Details for CVE-2025-14713

Vulnerability Analysis

The vulnerability stems from an exposed dangerous method or function within the C2 Identity Edge Server package. The edge server brokers identity operations between on-premises directories and Synology's C2 Identity cloud service. An interface intended for internal or privileged operations is reachable over the network without proper access controls.

The exposed function returns user credential material to the caller. Because the attack vector is network-based and requires no authentication or user interaction, any attacker with network reachability to the edge server can invoke the method. The impact is confined to confidentiality, with integrity and availability unaffected per the published CVSS vector.

Root Cause

The root cause is the inclusion of a sensitive method or endpoint within a network-exposed interface that lacks authentication, authorization, or sufficient input gating. This pattern, classified under [CWE-749], occurs when developers expose internal helper functions through a public API surface without applying access controls appropriate to the data those functions return.

Attack Vector

An attacker reaches the C2 Identity Edge Server over the network and invokes the exposed method. The server responds with credential data belonging to users registered on the edge server. No prior foothold, social engineering, or privileged context is required. Once credentials are obtained, the attacker can authenticate to identity-integrated services, escalate access, or pivot into federated SaaS resources. Refer to the Synology Security Advisory SA-25-18 for vendor-confirmed technical scope.

Detection Methods for CVE-2025-14713

Indicators of Compromise

• Unexpected inbound HTTP/HTTPS requests to C2 Identity Edge Server endpoints from external or unmanaged source IPs
• Authentication events for edge server users originating from geographies or hosts inconsistent with their normal pattern
• Outbound connections from the Synology DSM appliance to unrecognized hosts following edge server requests

Detection Strategies

• Inspect DSM and C2 Identity Edge Server application logs for requests to administrative or internal API paths from non-allowlisted clients
• Correlate edge server access logs with downstream authentication failures or successes across federated services
• Alert on credential reuse patterns where the same user account authenticates from multiple disparate sources within a short window

Monitoring Recommendations

• Forward DSM syslog and C2 Identity Edge Server logs to a centralized SIEM for retention and correlation
• Baseline normal API call patterns to the edge server and alert on deviations in request method, path, or source
• Monitor for spikes in 200-status responses on identity-related endpoints that historically saw low traffic volume

How to Mitigate CVE-2025-14713

Immediate Actions Required

• Upgrade the Synology C2 Identity Edge Server package on DSM to version 1.76.0-0307 or later without delay
• Restrict network reachability to the edge server using firewall rules that permit only required client subnets
• Rotate credentials for all user accounts managed through the affected edge server after patching
• Audit recent edge server access logs for evidence of credential extraction attempts predating the patch

Patch Information

Synology has released a fixed package version 1.76.0-0307 of the C2 Identity Edge Server for DSM. Apply the update through Package Center on affected DSM systems. Full remediation details are published in the Synology Security Advisory SA-25-18.

Workarounds

• Place the C2 Identity Edge Server behind a VPN or zero-trust network access gateway until patching is complete
• Block external access to the edge server's management and API ports at the perimeter firewall
• Disable the C2 Identity Edge Server package on DSM appliances that do not actively require edge identity brokering

# Example firewall restriction (iptables) limiting edge server access to a trusted subnet
iptables -A INPUT -p tcp --dport 443 -s 10.10.0.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP